Selection in plant populations of effectively infinite size. V. Biallelic models of trioecy

A one-locus two-allele model of trioecy (presence of hermaphrodites, males and females in one population) is considered, in order to study the conditions for the persistence of this system. All possible assignments of the three sex types to the three genotypes are considered. This leads to three different modes of inheritance of trioecy, namely (a) females heterozygous, (b) males heterozygous and (c) hermaphrodites heterozygous, where in each mode each of the remaining two sex types is homozygous for one of the alleles. For mode (c) trioecy is always persistent, and the dependence of the sex ratio (for the three sex types) on the ovule and pollen fertilities and on the hermaphrodite selfing rate is specified. For the other two modes, (a) and (b), trioecy is not protected, i.e., it may not persist for any fertilities, viabilities or selfing rates. Thus, in this situation it is important to study the conditions under which the "marginal" systems of sexuality of trioecy, i.e., hermaphroditism, dioecy and gynodioecy in mode (a), and hermaphroditism, dioecy and androdioecy in mode (b), may become established. The results show that each marginal system may evolve from each other via trioecy. The evolution of dioecy is easier in mode (a) than in (b), so that female heterogamety would be expected to occur more often than male heterogamety in the present model. Under some conditions the breeding system obtained in equilibrium populations may depend on the initial genotype frequencies.—The necessity of considering modes of inheritance for sexual polymorphisms is demonstrated by comparing our results with those obtained from an evolutionary stable strategy (ESS) analysis of a purely phenotypic model.     

The sea anemone Calliactis tricolor and its association with the Hermit crab Dardanus venosus

The association of certain sea anemones and hermit crabs is established in different ways according to the species involved. The present study shows that the behaviour patterns of the two partners in associations between Calliactis tricolor (Lesueur) and Dardanus venosus (H. M. Edwards) in the Caribbean are similar to those seen in the Mediterranean C. parasitica and D. arrosor .
Although about half the crabs display an active behaviour pattern in laboratory trials, the anemone frequently settles on shells unaided and most C. tricolor respond to molluscan shells by clinging with their tentacles until the pedal disc can be attached. As a rule it is necessary for the anemone to relax and to cling to the shell if the crab is to be successful in transferring the anemone to its shell.
The behaviour patterns of D. venosus include a distinctive tapping of the edge of the base of C. tricolor after which the anemone is pulled or lifted off and transferred to the shell. An experimenter can also cause the anemone to relax and to detach itself by tapping the edge of the base with plastic rods after the manner of the crab.
The mechanisms by which the tentacles of Calliactis cling to, and by which the base settles upon, shells still remain to be elucidated. The participation of nematocysts in these processes could not be demonstrated in this study.
C. tricolor is found on some other pagurid and non-pagurid crabs in various localities. These associations need to be investigated fully in order that the behaviour patterns of C. tricolor may be correctly interpreted and compared with those of other species of Calliactis .     

The 131I Ortho-iodohippurate Photoscan in Human Renal Allografts

Nine examples, in seven patients, from a large cadaver renal allograft program, illustrate the value of radio-hippuran photoscans in differentiating causes of post-implant oliguria. Hippuran scans are shown to be more valuable than chlormerodrin scans when renal function is acutely depressed. Hippuran scans aided in the decision to remove kidneys in four cases of severe oliguria and to retain kidneys in two others. In two further examples, extravasation of urine was detected by scanning after radio-hippuran injection when other tests had failed to do so.The technique of radio-hippuran scanning has a place in the differentiation of acute and subacute renal dysfunction and has proved particularly valuable in the early oliguric complications of a cadaver renal transplant program.     

Natural History of Isolated Patent Ductus Arteriosus and the Effect of Surgical Correction: Twenty Years' Experience at The Hospital for Sick Children,Toronto

Seven hundred and forty-four cases of patent ductus arteriosus were diagnosed at The Hospital for Sick Children, Toronto, in the 20-year period from 1947 to 1966. Of these 705 have been treated surgically. It is concluded that operation is best performed between 6 and 12 months of age. Isolated ductus arteriosus is rarely a cause of congestive heart failure, and is more likely to be so in the presence of the rubella syndrome. Failure associated with the anomaly in the neonatal period can usually be successfully managed by medical treatment. Spontaneous closure after one month of age is not to be expected. Surgical treatment at the appropriate time prevents the subsequent development of Eisenmenger''s complex.     

Neue oder wenig bekannte Flechten in der Tschechoslowakei. I

Es werden 28 Arten von lichenisierten Fungi (Flechten) mit kritischen taxonomischen Hinweisen oder Ergänzungen zu den in der Literatur vorhandenen Beschreibungen, oft mit chorologischen Bemerkungen und Angaben über die ökologischen Verhältnisse ihrer Standorte angeführt, von denen die nachgenannten Arten und Namenskombinationen neu sind:Verrucaria scabra Vězda sp. n.,Geisleria xylophila Vězda sp. n.,Toninia steineri Poelt etVězda sp. n.,Pachyascus byssaceus (Vězda) Vězda comb. n. undMicarea gomphillacea (Nyl.) Vězda comb. n.