The olivocerebellar projection to lobules I and II.

The olivocerebellar projection to lobules I and II was studied by means of retrograde transport from implants of the crystalline WGA-HRP complex. Retrogradely labelled neurons were found in the medial and dorsal accessory olives. Judged from the distribution of labelled cells, we conclude that parasagittally the olivocerebellar terminal zones A and B (i.e., the cerebellar cortical strips receiving axons from the olivary A and B regions) extend anteriorly into lobule Ia, whereas the fused olivocerebellar terminal C1/C3 zones reach lobule IIa. The olivocerebellar terminal C2 zone extends into lobule IIIa but not into lobule IIa. In lobule I the medial border of the B zone lies about 1 mm from the midline, in lobule II the B zone extends somewhat more medially. The lateral border of this zone is 1.9-2 mm from the midline. Compared to previous results, it appears that most of the Purkinje cells in lobule I projecting to the vestibular nuclei lie medially to the olivocerebellar terminal B zone.     

Organization of somatic nerve projections in various cortical areas of the cat cerebellum

We conducted a layer analysis of evoked potentials arising in various cortical cerebellar areas (vermis and intermediate zones of the anterior lobe, and the ansiform lobe) of non-anesthetized cats upon stimulation of nerves in fore- and hindlimbs. This analysis yielded the conclusion on the arrival of stimuli at the cerebellar cortex over two types of moss fibers innervating two types of granule cells which we described earlier. Impulses transmitted over type I moss fibers stimulate Purkinje cells. The activation of type II moss fibers has no immediate effect on these cells. Type I moss fibers terminate in the vermis and the intermediate zone of the hemispheres and do not terminate in the lateral hemispheric region. While projections of type I moss fibers are somatotopically organized in the intermediate zone they are diffuse in the vermis. Type II moss fibers terminate in all the regions of the crebellar cortex under study, but their projections show no somatotopic organization. The question of the afferent pathways terminating as type I and II moss fibers is discussed.Institute of Problems of Information Transmission, Academy of Sciences of the USSR, Moscow. M. V. Lomonosov Moscow State University. Translated from Neirofiziologiya, Vol. 3, No. 2, pp. 166–174, March–April, 1971.     

Observations on the projection from the perihypoglossal nuclei onto the cerebellum in the macaque monkey

The occurrence and distribution of retrogradely labeled cells in the perihypoglossal nuclei of the monkey were mapped after injections of horseradish peroxidase in various cerebellar cortical regions. In general the findings are in accord with those made in the cat. The flocculus receives a heavy bilateral projection from the nucleus prepositus, particularly from its caudoventral part, and from the nucleus of Roller. There is an apparently scanty projection from the nucleus intercalatus. The uvula receives a rather similar projection, but in the prepositus the cells projecting to the uvula are on the whole situated more dorsally and rostrally than those supplying the flocculus. The projection to lobules VII-VIII is distinct. More scanty projections have been found to the paramedian lobule and the anterior lobe. The different but partially overlapping sites of origin in the prepositus of fibers to the flocculus and uvula indicate the presence of a topical pattern within the perihypoglosso-cerebellar projection, as in the cat (34). In the monkey the two regions of origin appear to coincide with two particular cell collections in the prepositus (12). Both small and middle sized cells project to the cerebellum, as they do in the cat (9, 48). The nucleus supragenualis nervi facialis in the macaque is morphologically different from the corresponding nucleus in most other mammalian species (12), but it contains labeled cells after injections in the flocculus, uvula and other cerebellar regions. A considerable number of cells in the abducent nucleus are labeled after injections in the flocculus and the posterior vermis.     

Localization of 5-HT1A serotonin receptors in the cerebellum of young rats

Previous studies have shown that functional 5-HT_1A receptors are present in the cerebellum only for the early postnatal period in rats. In order to investigate further the possible physiological significance of such a transient expression of 5-HT_1A receptors during maturation of the cerebellum, anatomical studies were performed for identifying which cell type(s) are endowed with these receptors in 8-day-old rats. Autoradiography (using [¹²⁵I]BH-8-MeO-N-PAT) with dry films and emulsion-coated coverslips, and radioimmunohistochemistry (using specific polyclonal anti-5-HT_1A receptor antibodies) of vermis sections revealed that 5-HT_1A receptors were mainly concentrated in the molecular layer of the anterior part of the lobule X and the posterior part of the lobule IXB. X-Irradiation on the 5th postnatal day yielded an agranular cerebellum whose density of 5-HT_1A sites was higher than that in age-paired control animals. These data indicate that 5-HT_1A receptors are not located on granule cells, but probably on glial cells in the molecular layer of the immature cerebellum. This location further supports the possible implication of glial 5-HT_1A receptors in some trophic action of 5-HT during CNS maturation.     

Ectopic Purkinje-like cells are GABAergic: Immunohistochemistry with an immune serum against glutamic acid decarboxylase

Summary Intensely stained cells are found in the cerebellar white matter of the vermis and paravermis in adult rats after immunoreaction with an immune serum raised against glutamic acid decarboxylase (GAD). The cells are similar in size to cortical Purkinje cells and three times the size of Golgi cells of the internal granule layer, and have a thick immunopositive cell process emerging from a welldefined cytoplasmic cone. In the cytoplasm, immunoprecipitates are more dense around the nucleus as in normally located Purkinje cells. The morphological appearance of the immunopositive cells suggests that they may be ectopically located Purkinje cells. The soma of the ectopic Purkinje cells is contacted by a few darkly stained terminal boutons. Data indicate that, in spite of the different cellular environment, ectopic Purkinje cells can develop not only the typical morphological pattern already described but also other intrinsic features, such as their typical inhibitory neurotransmitter.     

The topographical localization of acetylcholinesterase in the adult rat cerebellum: A reappraisal

Summary The adult rat cerebellum has been investigated histochemically for acetylcholinesterase activity by the direct-coloring thiocholine technique. Results obtained are as follows:Staining indicative of sites of acetylcholinesterase (AChe) activity are predominantly delimited to the granular layer of the cerebellar cortex. The white matter directly adjacent to the granular layer of any lobule exhibit stronger activity than the medullary core. Often the molecular layer stain, diffusely and weakly.A great proportion of the enzyme staining is attributed to afferent mossy terminals. Golgi cells are also considered to possess intracellular AChe.Topographically, the vermian lobules of the cerebellum stain stronger relative to the hemispherical lobules except for the flocculus and paraflocculus. Mediolateral gradation of activity if present is not convincing. In the vermis, the lingula stains moderately. A distinctive feature of the present study is the enzyme activity in sub-lobuli VIb and VIc of the declive and the anterior portion of lobule VII. These areas stain densely and strongly. The nodule and lower part of the uvula exhibit dense and intense staining for AChe. All other lobules of the cerebellum stain weakly, more so those of the anterior lobe (besides the lingula).A rich core of AChe staining fibres radiate from the white matter adjacent to lobule X to reach lobules I, II, III, IV and V. A similarly intense core of AChe is found subjacent to the granular layer of lobules VI and VII.The three pairs of cerebellar peduncles stain differentially. Staining in the intracerebellar nuclei are however uniformly weak.The present findings are discussed as they relate to previous studies and in the light of current thoughts in cerebellar anatomy and function. Attention is drawn particularly to the functional implication of the dense and strong enzyme activity herein reported for the declive-tuber vermis complex of the cerebellum as these areas are believed to be sites of termination of cerebellar teleceptive inputs.     

LHRH-immunoreactive structures in the sheep brain

Neural structures containing luteinizing hormone-releasing hormone (LHRH) are characterized in adult ewe and female lamb brains. Three anti-LHRH antisera are used in an immunofluorescent or immunoperoxidase method. On our preparations, all three gave the same results, expressed as number of labelled cells (about 2500 in a whole brain). It was found that 95% of the LHRH-immunoreactive cells are located in the preoptico-hypothalamic area, where cell bodies are localized mainly (50%) in the area surrounding the organum vasculosum of the lamina terminalis (OVLT); they are also found in a more anterior section of the medial part of the olfactory tubercle and the medial septum (14%), in a more posterior situation in the anterior and lateral hypothalamus (16%), and in the mediobasal hypothalamus (15%). Fibres originating in various part of the whole preoptico-hypothalamic group reach the OVLT and the median eminence. The remaining cells (5%) and fibres are found in various tel-, di-, and mesencephalic areas.     

The projection of spinocerebellar neurons from the sacrococcygeal region of the spinal cord in the cat. An experimental study using anterograde transport of WGA-HRP and degeneration.

The projection from the sacro-coccygeal region of the spinal cord to the cerebellum was studied by two different techniques in the cat. In five cats wheat germ agglutinin-horseradish peroxidase conjugate (WGA-HRP) was injected caudal to a preceding unilateral cordotomy at the sacral level, aimed at interrupting the spinocerebellar tracts on one side completely, and the distribution of WGA-HRP labeled mossy fibers and mossy fiber terminals was studied in the cerebellum. In three additional cats, degenerating fibers were examined in Fink-Heimer stained sections following unilateral transection of the lateral and ventral funiculi at L7 or S3 level. In the WGA-HRP experiments the labeled mossy fiber terminals were located bilaterally in lobules I-V. Most of them were found in the anterior part of lobule II. In addition, labeled terminals were observed in sublobule VIIIB and in pars copularis of the paramedian lobule, contralateral to the cordotomy. The terminals in the anterior lobe were concentrated in longitudinal zones parallel to the mid sagittal plane. In lobule II, the terminals were most abundant in the superficial, apical parts of the folia. Some presumed terminals were also seen in the cerebellar nuclei. Labeled fibers were found contralateral, but not ipsilateral to the cordotomy in the superior and inferior cerebellar peduncles, as well as in the spinal cord rostral to the cordotomy. The results of the degeneration experiments were the same as those of the WGA-HRP experiments with regard to the detailed projections in the cerebellar cortex. This is strong support against the possibility that WGA-HRP labeled cerebellar mossy fiber terminals, following WGA-HRP injections in the spinal cord, would represent terminals of collaterals of retrogradely labeled neurons. It also lends strong support in favour of WGA-HRP as a reliable anterograde tracer for studying cerebellar cortical projections of spinocerebellar neurons in the cat.     

LHRH-immunoreactive structures in the sheep brain

Summary Neural structures containing luteinizing hormone-releasing hormone (LHRH) are characterized in adult ewe and female lamb brains. Three anti-LHRH antisera are used in an immunofluorescent or immunoperoxidase method. On our preparations, all three gave the same results, expressed as number of labelled cells (about 2500 in a whole brain). It was found that 95% of the LHRH-immunoreactive cells are located in the preoptico-hypothalamic area, where cell bodies are localized mainly (50%) in the area surrounding the organum vasculosum of the lamina terminalis (OVLT); they are also found in a more anterior section of the medial part of the olfactory tubercle and the medial septum (14%), in a more posterior situation in the anterior and lateral hypothalamus (16%), and in the mediobasal hypothalamus (15%). Fibres originating in various part of the whole preoptico-hypothalamic group reach the OVLT and the median eminence. The remaining cells (5%) and fibres are found in various tel-, di-, and mesencephalic areas.We would like to dedicate this work to the memory of Dr. M.P. Dubois     

Developmental studies on the loricate choanoflagellateStephanoeca diplocostata Ellis. V. The cytoskeleton and the effects of microtubule poisons

Summary InStephanoeca diplocostata microtubules are located in four positions namely: within the flagellar axoneme; just beneath the plasmalemma; associated with the silica deposition vesicles (SDVs) during early stages of costal strip deposition; and in the mitotic spindle. At the anterior end of the cell the 50–60 peripheral microtubules, which are organized more or less parallel to the long axis of the cell, converge around the base of the emergent flagellum. A short second flagellar base is positioned between the nucleus and the base of the emergent flagellum. Developing costal strips are located individually within SDVs in the peripheral cytoplasm. During the early stages of silica deposition each SDV is curved and subtended longitudinally on its concave side by two microtubules. When a costal strip has achieved sufficient rigidity to withstand bending the SDV-associated microtubules are depolymerized. Treatment of exponentially growing cells with sublethal concentrations of microtubule poisons, such as colchicine, podophyllotoxin, griseofulvin andVinca alkaloids depresses growth. Treatment with these drugs also affects the length and morphology of developing costal strips perhaps by interfering with the shaping and supporting functions of SDV-associated microtubules. Instead of being long and crescentic with a standard radius of curvature, costal strips of treated cells are usually short and misshapen, with irregular bends. After drug treatment, juveniles produced as a result of cell division do not develop flagella but can still assemble a lorica although it is usually misshapen. The role of microtubules and microfilaments in lorica production is discussed.     

独叶草叶二叉分枝脉序中网结脉和盲脉的形态学研究

对独叶草营养叶二叉分枝脉序及其中的网结脉和盲脉的形态学研究表明：(1)网结脉中2条完全汇合的与靠近脉中完全分离的叶脉之间未发现任何形式的维管束汇合的中间类型及网结脉中具有不同程度的连接脉退化痕迹的事实表明,网结脉不可能由靠近脉产生,相反,由于网结脉中联结脉的退化而形成开放脉;(2)盲脉是通过伴随着齿退化的达齿脉的退化、网结脉中联结脉的间断、非网结脉由分枝处间断三种方式产生的;(3)越裂片脉的出现及其可以形成网结脉的现象表明独叶草营养叶可能曾具有较为复杂的脉序,这种叶脉也呈现出退化的趋势;(4)独叶草营养叶的二叉分枝脉序可能是一种退化性状,而网结脉的出现可能是这种退化过程中的残留痕迹。     

A well defined spinocerebellar system in the weakly electric teleost fish Gnathonemus petersii. A tracing and immuno-histochemical study.

Long ascending fiber systems were investigated in the spinal cord of a teleost fish, Gnathonemus petersii. Concomitant results of Fink-Heimer degeneration tracing as well as CaBP28K immunohistochemical labelling demonstrate the existence of a well defined direct pathway from the very lowest spinal level to the caudal lobe of the cerebellum. HRP retrograde labelling shows that this pathway originates in a cellular column located in the most ventral part of the lateral column next to the lateral extremity of the ventral horn. From each spinal segment, the large axons of these cells gather and form a strip shaped tract at the periphery of the lateral column immediately dorsal to the cell column from which they originate. The spinal course of these fibers is ipsilateral; they give off a large number of collaterals to the lateral reticular nucleus. Bypassing the trigeminal motor nucleus, the lateral column tract courses dorsally to the paratrigeminal command associated nucleus between the lateral lemniscus and the nucleus preeminentialis and with a ventro-dorsally oriented large loop, turns in the caudal direction and penetrates into the cerebellar caudal lobe. Running caudally in the dorsal granular layer of the caudal lobe, it shifts more and more medially and crosses the midline whilst decussating with the contralateral tract on the dorsal margin of the molecular layer of the caudal lobe. Finally, the tract splits off and terminates throughout the granular layer of the caudal lobe. The main characteristics of this pathway are similar to those of the ventral spinocerebellar tract of higher vertebrates; it conveys information from all spinal levels directly to the contralateral cerebellum. However, it does not seem to receive direct synaptic input from the periphery, since projection of the dorsal root fibers appears to be limited to the dorsal ipsilateral half of the spinal cord. The appearance of such a pathway in a teleost fish is probably related to the existence of a well developed proprioceptive system in this species.     

Distribution of parasympathetic motoneurones in the oculomotor complex innervating the ciliary ganglion in the marmoset (Callithrix jacchus)

Parasympathetic motoneurones in the oculomotor complex which innervate the ciliary ganglion were identified using the horseradish peroxidase (HRP) retrograde axonal tracer technique. The ciliary ganglion was located behind the eye by a lateral orbital approach and injected with HRP pellets mounted on the tips of microelectrodes. Most of the labelled cells were distributed throughout the whole Edinger-Westphal nucleus (EW). Outside the EW, only a small number of labelled cells were found, and most of these were located in the median zone ventral to the EW. There was no evidence of a division of the EW into rostral and posterior subnuclei, nor for separate cell populations in the EW and the anterior median nucleus (AM), respectively. At rostral levels labelled cells were confined to the EW with no overlap into the AM. In contrast to most previous studies no labelled cells were found in the AM. The possible physiological functions of the EW and the ventral components of the EW are discussed.     

NOVEL PELLICLE SURFACE PATTERNS ON EUGLENA OBTUSA (EUGLENOPHYTA) FROM THE MARINE BENTHIC ENVIRONMENT: IMPLICATIONS FOR PELLICLE DEVELOPMENT AND EVOLUTION1

Euglena obtusa F. Schmitz possesses novel pellicle surface patterns, including the greatest number of strips (120) and the most posterior subwhorls of strip reduction in any euglenid described so far. Although the subwhorls form a mathematically linear pattern of strip reduction, the pattern observed here differs from the linear pattern described for Euglena mutabilis F. Schmitz in that it contains seven linear subwhorls, rather than three, and is developmentally equivalent to three whorls of exponential reduction, rather than two. These properties imply that the seven‐subwhorled linear pattern observed in E. obtusa is evolutionarily derived from an ancestral bilinear pattern, rather than from a linear pattern, of strip reduction. Furthermore, analysis of the relative lateral positions of the strips forming the subwhorls in E. obtusa indicates that (1) the identity (relative length, lateral position, and maturity) of each strip in any mother cell specifies that strip’s identity in one of the daughter cells following pellicle duplication and cell division, (2) the relative length of any given pellicle strip regulates the length of the nascent strip it will produce during pellicle duplication, and (3) pellicle pores develop within the heels of the most mature pellicle strips. These observations suggest that continued research on pellicle development could eventually establish an ideal system for understanding mechanisms associated with the morphogenesis and evolution of related eukaryotic cells.     

A model for the morphogenesis of strip reduction patterns in phototrophic euglenids: evidence for heterochrony in pellicle evolution

We propose a general developmental model that explains the evolutionary origin, diversification, and inheritance of pellicle strip patterns in phototrophic euglenids. Dividing cells of Euglena gracilis, E. viridis, and Phacus similis were observed with scanning electron microscopy in order to study the morphogenesis of posterior whorls of strip reduction. We found evidence that constant whorl numbers are maintained through cell division because of organized strip growth before and during cytokinesis. Alternating nascent strips form a new whorl of strip reduction at each of the anterior and posterior ends of daughter cells. Strips that terminated to form posterior whorls in the mother cell change in length during the development of daughter cells. In the mother cells of E. gracilis, the strips forming whorls I and II grow to become whorls II and III, respectively, in the daughter cells; the strips forming whorl III in the mother cell lengthen and meet with other strips already present at the posterior tip of daughter cells. This process of whorl morphogenesis during asexual reproduction is consistent with known variation in pellicle strip patterns and suggests that heterochrony played a major role in the ultrastructural evolution of phototrophic euglenids.     

Comparative morphology of the euglenid pellicle. I. Patterns of strips and pores

In anticipation that improved knowledge of euglenid morphology will provide robust apomorphy-based definitions for clades, transmission and scanning electron microscopy were used to reveal novel morphological patterns associated with the euglenid pellicle. In some taxa, the number of pellicle strips around the cell periphery reduces as discrete whorls at the anterior and posterior ends of the cell. The number of whorls at either end varies between selected euglenid taxa but is invariant within a taxon. The pattern of strip reduction associated with these whorls is shown to have at least three evolutionarily linked states: exponential, pseudoexponential, and linear. Two general equations describe these states near the posterior end of euglenid cells. Exponential patterns of strip reduction near the anterior end are described by a third equation. In addition, several euglenid taxa were found to possess conspicuous pellicle pores. These pores are arranged in discrete rows that follow the articulation zones between adjacent strips. The number of strips between rows of pores varies between taxa and displays a series of consecutive character states that differ by a power of two. The patterns of pores may not only have phylogenetical and taxonomical value but may provide morphological markers for following strip maturation during cytoskeletal reproduction.     

Regional differences in the ultrastructure of Purkinje cells of the rat

Summary In the albino rat, perikaryal diameter, volume density of the granular endoplasmic reticulum and Golgi apparatus, and lumenal diameter of cisternae of the granular endoplasmic reticulum are larger in Purkinje cells of lobule Via (neocerebellum) than in those of lobule X (archicerebellum). In contrast, only the surface density of cisternae of the granular endoplasmic reticulum is larger in Purkinje cells of lobule X. The cisternae of granular endoplasmic reticulum are arranged into conspicuous Nissl bodies parallel to the nuclear membrane, but the content of ribosomes and polysemes is markedly less in lobule-X cells than in cells from lobule VI a. These results indicate qualitative and quantitative differences between the metabolically important organelles in Purkinje cells of the neo- and archicerebellum (cf. Larsell 1952).Supported by a grant from the Deutsche Forschungsgemeinschaft (La 184/7)     

Mouse Model Reveals the Role of RERE in Cerebellar Foliation and the Migration and Maturation of Purkinje Cells

Nuclear receptors and their coregulators play a critical role in brain development by regulating the spatiotemporal expression of their target genes. The arginine-glutamic acid dipeptide repeats gene (Rere) encodes a nuclear receptor coregulator previously known as Atrophin 2. In the developing cerebellum, RERE is expressed in the molecular layer, the Purkinje cell layer and the granule cell layer but not in granule cell precursors. To study RERE''s role in cerebellar development, we used RERE-deficient embryos bearing a null allele (om) and a hypomorphic allele (eyes3) of Rere (Rere ^om/eyes3). In contrast to wild-type embryos, formation of the principal fissures in these RERE-deficient embryos was delayed and the proliferative activity of granule cell precursors (GCPs) was reduced at E18.5. This reduction in proliferation was accompanied by a decrease in the expression of sonic hedgehog (SHH), which is secreted from Purkinje cells and is required for normal GCP proliferation. The maturation and migration of Purkinje cells in Rere ^om/eyes3 embryos was also delayed with decreased numbers of post-migratory Purkinje cells in the cerebellum. During the postnatal period, RERE depletion caused incomplete division of lobules I/II and III due to truncated development of the precentral fissure in the cerebellar vermis, abnormal development of lobule crus I and lobule crus II in the cerebellar hemispheres due to attenuation of the intercrural fissure, and decreased levels of Purkinje cell dendritic branching. We conclude that RERE-deficiency leads to delayed development of the principal fissures and delayed maturation and migration of Purkinje cells during prenatal cerebellar development and abnormal cerebellar foliation and Purkinje cell maturation during postnatal cerebellar development.     

Regional differences in the distribution of golgi cells in the cerebellar cortex of man and some other mammals

Summary The number of Golgi cells per unit volume was determined in different regions of the cerebellar cortex of man and of ten other mammals. Despite the general belief in the uniform architecture of the cerebellar cortex, regional differences in the distribution of Golgi cells were found. In the inferior parts of the vermis, the number of Golgi cells per unit volume is twice that in the corresponding hemispheres. In addition, there are differences between the anterior and inferior parts of the vermis. These differences are a feature of the cytoarchitecture of the cerebellum in man and all the investigated mammals. The ratio of Purkinje cells to Golgi cells was also determined and found to differ in different species. In man, this ratio is 11.5, while in the monkey and cat it is almost 11.9 and in the rat 13.3. These differences in the ratio of Purkinje cells to Golgi cells are discussed from the point of view of cerebellar evolution.Supported by the Deutsche Forschungsgemeinschaft.     

Retinopetal neuronal system in the brain of an air-breathing teleost fish,Channa punctata

Summary Retinopetal neurons were visualised in the telencephalon and diencephalon of an air-breathing teleost fish, Channa punctata, following administration of cobaltous lysine to the optic nerve. The labelled perikarya (n=45–50) were always located on the side contralateral to the optic nerve that had received the neuronal tracer. The rostral-most back-filled cell bodies were located in the nucleus olfactoretinalis at the junction between the olfactory bulb and the telencephalon. In the area ventralis telencephali, two groups of telencephaloretinopetal neurons were identified near the ventral margin of the telencephalon. The rostral hypothalamus exhibited retrogradely labelled cells in three discrete areas of the lateral preoptic area, which was bordered medially by the nucleus praeopticus periventricularis and nucleus praeopticus, and laterally by the lateral forebrain bundle. In addition to a dorsal and a ventral group, a third population of neurons was located ventral to the lateral forebrain bundle adjacent to the optic tract. The dorsal group of neurons exhibited extensive collaterals; a few extended laterally towards the lateral forebrain bundle, whereas others ran into the dorsocentral area of the area dorsalis telencephali. A few processes extended via the anterior commissure into the telencephalon ipsilateral to the optic nerve that had been exposed to cobaltous lysine. However, the ventral cell group did not possess collaterals. In the diencephalon, retinopetal cells were visualised in the nucleus opticus dorsolateralis located in the pretectal area; these were the largest retinopetal perikarya of the brain. The caudal-most nucleus that possessed labelled somata was the retinothalamic nucleus; it contained the largest number of retinopetal cells. The limited number of widely distributed neurons in the forebrain, some with extensive collaterals, might participate in functional integration of different brain areas involved in feeding, which in this species is influenced largely by taste, not solely by vision.