Influence of honey and maternal age on egg load of lab-cultured <Emphasis Type="Italic">Cotesia marginiventris</Emphasis>

Laboratory experiments were conducted to determine the impact of feeding status and maternal age on egg load of Cotesia marginiventris (Cresson) (Hymenoptera: Braconidae), a solitary, koinobiont endoparasitoid of noctuid pests. Egg load was defined as the number of mature (i.e., fully-chorionated) eggs found in the ovaries and oviducts. Significantly more mature eggs were stored in honey-fed than starved females. For honey-fed females, egg load increased within several days of isolation from hosts. This study suggests that C. marginiventris is weakly synovigenic because females emerge with a considerable number of mature eggs and are capable of maturing many more eggs. Feeding on a suitable source of carbohydrate should increase the egg load (i.e., potential fecundity) of this insect within 3–4 days in an in vivo rearing system.     

Oviduct development inDrosophila

Summary The lateral oviducts ofDrosophila virilis were investigated in normal unoperated adult females, after unilateral and bilateral ovariectomy, and following the transplantation of genital discs. Subsequent to unilateral ovariectomy at larval stages of development, mature adult females exhibited reproductive systems with a free lateral oviduct which appeared somewhat shorter and less distended than a lateral oviduct normally attached to an ovary. Histological examination revealed that such free lateral oviducts have undergone considerable growth and differentiation in the absence of direct ovarian attachment, but exhibited a smaller lumen and more highly folded epithelium. They may be distinguished from attached lateral oviducts by conformational differences and by a possibly lesser size of the epithelial cells. Free lateral oviducts observed among bilaterally ovariectomized and sham-ovariectomized specimens were indistinguishable from those obtained after unilateral ovariectomy. The results are at variance with the previously accepted conclusion that oviduct growth inDrosophila is dependent upon inductive influences emanating from the ovary and directing the outgrowth of the oviducts. Differences in the developmental performance of the oviducts as a function of age at the time of ovariectomy were not evident in the study which included larvae ranging from the second instar to late in the third instar. Transplants of larval female genital discs to other larvae revealed a lesser development of the lateral oviducts than that exhibited by a genital disc developingin situ. A range of oviducal growth which lacked any relation to ovarian influences or to other internal organs of the hosts was obtained. In general, decreased amounts of oviducal muscle were found associated with the transplants.Presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the University of Virginia. This investigation was supported in part by: a National Science Foundation Co-operative Fellowship, by the United States Public Health Service Predoctoral Grant 1F1-GM 19,262-1, and by a Summer Research Grant, University of Missouri-St. Louis.     

Ultrastructure and resistance to water loss in eggs of Acanthoscelides obtectus Say (Coleoptera: Bruchidae)

The mature oöcyte of Acanthoscelides obtectus is surrounded by three envelopes: an external layer, a chorion and a vitelline membrane. The external layer is secreted by the walls of the lateral oviducts. The chorion and vitelline membrane are secreted by the follicular cells. The vitelline membrane becomes very compact during the hour following fertilization and laying. The chorion is composed of three layers, one of which has a paracrystalline ultrastructure.Mature, unfertilized, chorion-containing oöcytes, whose vitelline membranes are loose, dehydrate rapidly in a dry atmosphere after laying or after removal from the lateral oviducts. Fertilized eggs are quite resistant to desiccation: after 12 days at 25°C and 5% relative humidity, viable larvae are obtained.The compact vitelline membrane is the most effective protection against dehydration. The chorion and the external layer are much less effective in preventing water loss from the egg.The retention of eggs in the lateral oviducts does not seem to lead to any modification of the structure of their envelopes.     

Oviposition in Cryptolaemus montrouzieri stimulated by wax filaments of its prey

The oviposition responses of Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae) to the soft scale Eupulvinaria hydrangeae (Steinweden) (Homoptera: Coccidae) and to the mealybug Planococcus citri (Risso) (Homoptera: Pseudococcidae) have been compared in the laboratory. The females delay oviposition and withhold mature eggs in their lateral oviducts in the absence of wax filaments produced by the prey (only present in the ovisac of E. hydrangeae, present in all stages of P. citri). Contact chemical cues perceived by females when probing the wax filaments with their mouthparts are the signals inducing the search for oviposition sites. The second step is under the control of the ovipositor by which females locate confined sites to lay eggs. This oviposition behaviour could have a considerable impact on the prey exploitation strategy of this important biocontrol agent and might help to understand its apparent ineffectiveness in situations of low prey density.     

Genesis of the reproductive system of mosquitoes. I. Female of Aedes stimulans (Walker)

The feminine dimorph has unique structures that produce eggs, select salubrious sites for the offspring, store sperm, and void the eggs. This paper provides a time table for development of these parts in Aedes stimulans based on preparations examined at 5-hour intervals when reared at 21°C. All growths of imaginal parts proceeds independent of activities in the larval tissues. Ovaries produce the eggs in terminal follicles of the ovarioles. Besides ovarioles each ovary contains sheaths for the ovarioles, pedicels attaching them to a central canal, the calyx, ovarian sheath and muscles. Ovaries are recognizable in newly hatched larvae as caps of cells on larger masses which become part of the delivery system for eggs. Each ovary grows forward from its attachment first as a column of cells that differentiates into the several tissues by the time the insect enters pupal life. Prior accounts have considered the ovary as the whole mass of cells on each side of the hemocoel of segment 6. Only the most anterior cells recognizably distinct at the end of embryogeny are generative. The delivery system for eggs is composed of the lateral oviducts and median or common oviduct. Primordia from which the former are derived are present from the end of embryogeny and throughout larval life as two distinct parts. Two ovoid masses occur in the hemocoel of segment 6. To each of these is attached a filament extending backward to an attachment ventrally and caudally in segment 7. They are rapidly changed into definitive lateral oviducts late in pupal life. The single primordium for generating the median genital tract appears during instar 3 as a caudal ventral plate of cells in segment 8 between a pair of bilateral buds and invaginates during instar 4 to form (1) the common oviduct from a midventral pouch, (2) three spermathecae from two lateral invaginations and (3) the elaborate vaginal area. The bilateral buds form no parts of the female. The post-vaginal area or atrium with its accessory organs is derived in part from the ventral plate of segment 8 and that of segment 9. The imaginal disc in segment 9 is present at the end of embryogeny as primordial buds and ventral plate and development is delayed until early pupal life when it projects inward to form part of the atrium and pouches once to form the common opening for the duct of the accessory gland and the canal to the bursa copulatrix. The buds of this disc produce no feminine parts. During the second larval instar lateral primordia appear as a pair of shields in the anal segment. They develop slowly until pupation when they extend caudally as two flaps called “cerci” in culicid literature and this paper.     

A glycoprotein of oviductal origin alters biochemical properties of the zona pellucida of hamster egg

Eggs were isolated from ovaries and oviducts of the golden hamster and the components of zonae pellucidae were examined using density gradient SDS-polyacrylamide electrophoresis. Zonae of ovarian eggs (ZP-OVA) had three major components corresponding to the so-called ZP-1, ZP-2, and ZP-3. Zonae of recently ovulated eggs collected from oviducts (ZP-OVI) had a 200–240 K component (ZP-O) in addition to the three components present in ZP-OVA. When ovarian and oviductal eggs were stained with FITC-conjugated B. simplicifolia-1 lectin (BS-1), which specifically binds to alpha-D-galactose- or alpha-N-acetyl-D-galactosamine-like terminal saccharide residues, ZP-OVI was intensely stained, while ZP-OVA was not. ZP-OVA gained the ability to bind to BS-1 after a brief treatment with oviduct extracts. These results suggest that biochemical properties of hamster zonae change after transport of eggs from ovary to the oviduct. The addition of the 200–240 K component of oviductal origin to preexisting zona components seems to be responsible for this change.     

Egg dumping by predatory insects

Synovigenic insects resorb oocytes when food is scarce and mature oocytes when food is plentiful. These two antagonistic processes allow an optimal allocation of resources to reproduction and somatic functions. Unlike hymenopteran parasitoids, ladybirds cannot resorb mature oocytes present in the oviducts. Is the energy contained in these oocytes lost or is there a mechanism for recovering it when needed? Females of two species of ladybird beetles Adalia bipunctata (L.) and Adalia decempunctata (L.) that are starved for >24 h lay single infertile eggs, which they immediately eat, and these eggs comprise the mature oocytes in the oviducts at the onset of starvation. This behaviour has some similarities to egg dumping reported in herbivorous insects and is part, in ladybird beetles, of a process to retrieve energy invested in reproduction. Such behaviour may exist in other predatory synovigenic insects species that do not invest in maternal care.     

Native vitellins are modified during ovarian development in the stick insect Carausius morosus (Br.)

Vitellins from ovarian follicles and newly laid eggs of the stick insect Carausius morosus were examined by ion exchange chromatography on a HPLC Mono Q column. Under these conditions, vitellins from newly laid eggs resolved as two distinct peaks, referred to as VtA and VtB, that eluted at 8.5 and 12.0 min, respectively. On native gels, both VtA and VtB separated into two different variant forms (VtA′ and VtA′, VtB′ and VtB′). By two-dimensional gel electrophoresis, VtA′ and VtA′ were shown to contain polypeptides A₁, A₂ and A₃. On the other hand, VtB′ and VtB′ appeared to comprise polypeptides B₁ and B₂ and B₁, A₁, A₂, B₂ and A₃*, respectively. A similar Vt polypeptide composition was also observed by size-exclusion chromatography of vitellins from newly laid eggs. Vitellins from early vitellogenic ovarian follicles resolved into a single chromatographic peak at 7.5 min that coeluted with a major peak from the hemolymph of egg-laying females. Ovarian follicles progressively more advanced in development exhibited a more complex chromatographic profile, consisting of three separate peaks. By two-dimensional gel immunoelectrophoresis, vitellins from ovarian follicles appeared to consist of two closely related, immunologically cross-reacting antigens that gradually shifted apart as ovarian development proceeded to completion. By size-exclusion chromatography, each Vt from ovarian follicles was shown to consist of a unique set of polypeptides different from those listed above. Single ovarian follicles were fractionated into yolk granules and yolk fluid ooplasm and tested by immunoblotting against Mab 12. Under these conditions, VtA variant forms in yolk granules and yolk fluid ooplasm reacted differently. Sections from ovarian follicles in different developmental stages were exposed to Mab 12 and stained with a peroxidase-conjugated, goat anti-mouse antibody. Regardless of the developmental stage attained, staining for peroxidase was restricted to free yolk granules, suggesting that native vitellins in stick insects are structurally modified upon fusion into the yolk fluid ooplasm. Arch. Insect Biochem. Physiol. 36:335–348, 1997. © 1997 Wiley-Liss, Inc.     

Hormonal control of locust oviducts

The oviducal muscles of the locust, Locusta migratoria, contract in a spontaneous and rhythmic fashion when isolated from the central nervous system. Hemolymph of ovipositing females, when added to isolated locust oviducts, altered the spontaneous contractility of the oviduct. This response was not evident after addition of hemolymph from a nonovipositing female and was still present after addition of the α-aminergic receptor antagonist, phentolamine. Oviducts in which mature eggs were present responded to homogenates of the corpus cardiacum by increasing both the frequency and amplitude of muscular contraction, whereas oviducts devoid of eggs showed no response. Extracts of ventral nerve cord also increased the spontaneous activity of the oviduct musculature. Although the muscles of the oviduct responded to homogenates of the brain, this response differed in two ways from the response due to corpus cardiacum homogenates. First, oviducts devoid of mature eggs responded to brain homogenates; and second, the response caused by the brain homogenates could be eliminated by the addition of 1 μM phenoxybenzamine. The significance of these results is discussed.     

柑桔爆皮虫卵巢发育动态

本研究利用室内饲养成虫,对柑桔爆皮虫的蛹及正常取食和交配、正常取食但未交配以及正常交配但未取食三种处理的雌成虫的卵巢发育进行了系统观察。结果显示：该虫具有1对卵巢,每侧有5根卵巢管。前两种处理的雌虫卵巢管均能正常发育,成虫寿命在30天左右; 没有取食的雌虫寿命只有7天左右,在其卵巢管的生长区和成熟区均无卵形成。根据卵巢的形状、卵的产生过程、卵巢萼内有无卵粒以及卵黄沉积情况等将卵巢发育程度分为6个级别,即发育初期（0级）、卵黄沉积前期(Ⅰ级)、卵黄沉积期(Ⅱ级)、成熟待产期(Ⅲ级)、产卵盛期(Ⅳ级)和产卵末期(Ⅴ级)。每头雌虫最高怀卵量在140粒左右,根据雌虫怀卵量变化趋势,推测正常取食和交配的柑桔爆皮虫雌虫在出孔后10天左右开始产卵,产卵历期可达22天左右。据此提出该虫卵巢管发育到成熟待产期(Ⅲ级)之前（即羽化出孔后10天之内）为出孔成虫的防治适期。     

Amino acid cues emanating from Pacific salmon eggs and ovarian fluid

The eggs of salmonid fishes are an important food source for many aquatic predators that detect eggs using olfaction. Moreover, chemicals from eggs and ovarian fluid aid sperm cells in detecting and locating eggs for fertilization, and ovarian fluid is attractive to conspecific males. Thus chemicals from eggs and ovarian fluid may facilitate reproduction but may also attract egg predators. The authors sampled mature females of three Pacific salmon species – Chinook (Oncorhynchus tshawytscha), coho (Oncorhynchus kisutch) and sockeye (Oncorhynchus nerka) – and determined the proportional representation of amino acids, potent fish odorants, from their eggs and ovarian fluid (Chinook and coho salmon only). They then tested juvenile coho salmon, an egg predator, for responses to ovarian fluid and egg odours using the electro-olfactogram (EOG) recording technique. The amino acid compositions of the salmon species were significantly and positively correlated with each other, and the interspecific differences were comparable to those between individuals of the same species. The egg water samples were, on average, dominated by lysine, alanine and glutamine (12.6%, 12.4% and 10.9%, respectively). The ovarian fluid samples were dominated by lysine (20.5%), followed by threonine (9.7%), glycine (9.2%) and arginine (8.8%). EOG recordings demonstrated the ability of juvenile coho salmon to detect the chemical traces of eggs and ovarian fluid. It is concluded that salmon eggs are a potent source of odours for potential predators but likely not highly differentiated among salmon species.     

Experiments inducing prospective polar body nuclei to participate in embryogenesis of the sawfly Athalia rosae (Hymenoptera)

Summary Mature eggs dissected from ovaries of unmated females of Athalia rosae (Hymenoptera: Tenthredinidae), if placed on a filter-paper soaked with distilled water, are activated and develop to haploid males. Occasionally, however, diploid females develop from these artificially activated eggs. Treatment of mature unfertilized eggs dissected from diploid females with ice-cold temperatures immediately before activation and with a high temperature (36° C) upon and immediately after activation resulted in the production of diploid males, diploid females, triploid females and gynandromorphs at high frequency. The same treatment of mature unfertilized eggs dissected from triploid females resulted in the production of only triploid survivors. These results, together with the results on the segregation of a marker mutation, yellow fatbody (yfb), appear to indicate that meiotic divisions were complete in the treated eggs, and that all four nuclei became potentially capable of participating in development with or without automictic fusion.Studies on the sawfly, Athalia rosae (Insecta, Hymenoptera, Tenthredinidae), part V     

Geographic parthenogenesis and the common tea‐tree stick insect of New Zealand

Worldwide, parthenogenetic reproduction has evolved many times in the stick insects (Phasmatidae). Many parthenogenetic stick insects show the distribution pattern known as geographic parthenogenesis, in that they occupy habitats that are at higher altitude or latitude compared with their sexual relatives. Although it is often assumed that, in the short term, parthenogenetic populations will have a reproductive advantage over sexual populations; this is not necessarily the case. We present data on the distribution and evolutionary relationships of sexual and asexual populations of the New Zealand stick insect, Clitarchus hookeri. Males are common in the northern half of the species’ range but rare or absent elsewhere, and we found that most C. hookeri from putative‐parthenogenetic populations share a common ancestor. Female stick insects from bisexual populations of Clitarchus hookeri are capable of parthenogenetic reproduction, but those insects from putative‐parthenogenetic populations produced few offspring via sexual reproduction when males were available. We found similar fertility (hatching success) in mated and virgin females. Mated females produce equal numbers of male and female offspring, with most hatching about 9–16 weeks after laying. In contrast, most eggs from unmated females took longer to hatch (21–23 weeks), and most offspring were female. It appears that all C. hookeri females are capable of parthenogenetic reproduction, and thus could benefit from the numerical advantage this yields. Nevertheless, our phylogeographic evidence shows that the majority of all‐female populations over a wide geographic area originate from a single loss of sexual reproduction.     

Structure of the ovaries in larvae and mature females of euholognathan stoneflies (Plecoptera)

The morphology of ovaries, oviducts and egg capsules in four species of euholognathan stoneflies was investigated. The characteristic features found were as follows: (i) numerous, long ovarioles, that open individually to the extensively folded, lateral oviducts; (ii) a thin, morphologically undifferentiated chorion; (iii) a thick gelatinous layer (extrachorion) which acts as an adhesive layer fixing the eggs to the substrate. Additionally, in the larval ovariole of Leuctra sp. the terminal filament anlage and clusters of germ cells have been found. These observations are in agreement with the classification of stonefly ovaries as primary (true) panoistic.     

Partial localization of a brain factor inhibiting egg production in the blood-feeding insect,Rhodnius prolixus

A previous study by Davey [Can J Zool 4:243–249 (1987)] showed that egg production in the blood-feeding insect Rhodnius prolixus is greatly enhanced when the corpus allatum (CA) is denervated. This result supported findings of others that the brain of Rhodnius imposes an inhibition on the CA via its connections to the CA. The present study identifies the nervus corporis cardiacum II (NCCII) as the nerve responsible for this inhibitory influence. Transecting the NCCII before feeding causes a dramatic increase in the number of eggs made. Since the NCCII is a relatively small nerve that may contain only axons of lateral and posterior neurosecretory cells in the protocerebrum, this result suggests that one or both of these cell types produce the brain factor inhibiting egg production in this insect. Arch. Insect Biochem. Physiol. 39:126–131, 1998. © 1998 Wiley-Liss, Inc.     

Morphological study of the reproductive system and ovarian growth of the univoltine bamboo borer,Omphisa fuscidentalis (Hampson, 1896) (Lepidoptera: Crambidae)

ABSTRACT

The female reproductive system and protein deposition in the ovaries during development have never been examined in the bamboo borer Omphisa fuscidentalis Hampson. The aim of this study was thus to study the morphology of the female reproductive system of each stage of development. The female reproductive system of the borer consists of a pair of ovary, oviduct and accessory glands. Each ovary is composed of four polytrophic ovarioles that connect to lateral oviducts, fused with a common oviduct. The size of the ovary in diapausing larvae for 9 months was determined. The length and width of the ovaries were the smallest in September larvae (0.343 ± 0.03 and 0.071 ± 0.01 mm, respectively). The ovaries were the largest during ovarian development in May (0.752 ± 0.08 mm long and 0.084 ± 0.01 wide). Additionally, ovarian size was significantly larger in adults than in pupae. The ovarian protein concentration of larvae in May was 0.59 ± 0.06 mg/ml and increased to 16.61 ± 7.5 and 37.42 ± 5.5 mg/ml in pupae (June) and adults (July), respectively. The results showed ovarian development in all life stages of this holometabolous insect, which has a longer life cycle than other lepidopterans.

Abbreviation: TEM: transmission electron microscope     

Mature egg number influences the behavior of femaleBattus philenor butterflies

Although oviposition behavior of butterflies has been studied extensively, physiological parameters that may affect various aspects of female behavior have been overlooked almost completely. The number of mature eggs carried by a female Battus philenorgreatly affects her behavior at any particular time. Females with many eggs search significantly more for host plants than females with fewer eggs, which tend to rest more. Parameters affecting the number of mature eggs are also studied.     

EGG ACTIVATION AND PARTHENOGENETIC REPRODUCTION IN INSECTS

1. Many insects reproduce by parthenogenesis. In one of the largest orders of the animal kingdom, the Hymenoptera, most of its members reproduce by arrhenotokous parthenogenesis. Egg activation in parthenogenetic animals obviously cannot be caused by fertilization of the egg. The question of what initiates egg development in parthenogenetically reproducing animals has been studied for a few insect species and is discussed in this article. 2. The grasshopper Melanoplus differentialis is one of several Orthoptera displaying accidental parthenogenesis. In this species, egg laying provides the stimulus to the completion of meiosis and start of embryonic development in unfertilized and probably also in fertilized eggs. The same holds true for the dipteran insect Drosophila melanogaster which exhibits rudimentary parthenogenesis, and for D. mercatorum showing accidental parthenogenesis. The precise way in which oviposition affects the egg is unknown. 3. The stick insect Carausius morosus reproduces by obligatory thelytoky. The triggering factor for removal of the meiotic block and initiation of embryonic development is oxygen from the air which penetrates to the egg through the micropyle immediately after oviposition. The oviposition act itself is not necessary for activation of the egg. 4. Comparative studies of the different types of oogenesis in the dipteran insect Heteropeza pygmaea show that in paedogenetically developing follicles meiotic arrest in prophase is of very short duration and a meiotic block at the end of oogenesis is absent. It is suggested that in this case triggering events for egg development are dispensable. On the other hand, under certain experimental conditions a meiotic block can be established in some of these follicles. 5. Investigations on the Ichneumonid wasp Pimpla turionellae have shown that unfertilized, male-determined eggs - and most likely also fertilized, femaledetermined eggs - are activated by mechanical stress exerted on the eggs during natural or imitated oviposition. This mechanical stress, in addition, activates a streaming system which is independent of meiotic completion and nuclear multiplication. Egg activation by egg distortion is also found in the Pteromalid species Nasonia vitripennis and occurs presumably in many other Hymenoptera. 6. Carausius morosus, Pimpla turionellae and Nasonia vitripennis are species with parthenogenetic reproduction for which the natural factors responsible for the initiation of egg development have been identified. The cases of Pimpla turionellae and Nasonia vitripennis are of particular interest because of the feasibility of artificially imitating the natural activating mechanism. 7. It is concluded that apart from fertilization various events at oviposition may trigger egg development. In addition, the occurrence of rudimentary parthenogenesis in many sexually reproducing animal species suggests that sperm entry and fertilization may frequently be necessary for the continuation of egg development rather than for its initiation.     

Spontaneous and neurally evoked contractions of visceral muscles in the oviduct of Locusta migratoria

The oviducts of Locusta migratoria are innervated by a pair of nerves which arise from, the seventh abdominal ganglion. A distinctive network of striated muscle fibres occurs in the oviducts. The lateral oviducts and common oviduct consist of an inner circular layer of muscle and an outer longitudinal layer of muscle. At the junction of the lateral and common oviduct an additional thin longitudinal layer is found adjacent to the basement epithelium. The oviducts contracted spontaneously when isolated from the central nervous system. These myogenic contractions took the form of peristaltic contractions in the lateral oviduct, and intermittent phasic-like contractions of the posterior regions of the lateral oviduct and the common oviduct. These phasic-like contractions were associated with individual complex potentials recorded extracellularly from the muscle fibres. In locusts that had been interrupted in the process of egg laying, there were large-amplitude action potentials, firing in a bursting pattern, in the oviducal nerves. These large action potentials were absent in locusts that had not been egg-laying. These action potentials were associated with both bioelectric potentials and mechanical events in the posterior region of the lateral oviduct and the common oviduct. Electrical stimulation of the oviducal nerve mimicked the effects of spontaneous action potentials, resulting in the appearance of monophasic potentials and contractions. The contractions were graded and dependent upon both frequency and duration of stimulation. It is concluded that the oviducts of Locusta are both myogenic and neurogenic. The role of these contractions in oviposition is discussed.     

The nerve fibres controlling the gonadotropic activity of the hypophysis of Rana temporaria

Summary In 27 adult female specimens of Rana temporaria, the total interruption of the nervous pathways to the median eminence and the hypophysis was performed, without disturbing the normal blood supply of the hypophysis. In eight cases this complete interruption persisted three months after operation. In these animals there occurred no seasonal development of the eggs, ovaries and oviducts. In the 19 other operated animals a varying degree of regeneration of the interrupted nerve fibres occurred. In these animals a varying number of ripe eggs was present, but in many of them there existed a significant difference between the weight of their ovaries compared with that of the ovaries of the control animals. In all control animals the seasonal development of the ovaries and oviducts was normal. From these and from previous experiments it could be concluded that the A. F. negative nerve fibres of the median eminence, not originating from the magnocellular neurosecretory preoptic nuclei, are responsible for the normal seasonal development of the ovaries and oviducts in Rana temporaria. It must be these nerve fibres that release gonadotropic releasing factors into the blood capillaries of the median eminence. The A. F. positive neurosecretory fibres, the portal circulation of the pars distalis and the pituicytes of the median eminence play only a secondary part during this period of control of the gonadotropic activity of the hypophysis.