Carpenter : Zoology at the British Associatio7i. 



44S 



on Monday, 7th September, opened by Mr. L. Doncaster, and 

 continued by Miss N. M. Stevens, Mr. W. Heape, F.R.S., and 

 Professor W. Bateson, F.R.S. Mr. Doncaster, from breeding 

 •experiments with the common Magpie Moth (Abraxas grossu- 

 lariata), and its variety ladicolov, concludes that ' sex 

 determinants behave as Mendehan characters, maleness and 

 femaleness being allelomorphic with one another, and 

 femaleness dominant. All females are heterozygotes, carrying 

 recessive maleness, and producing male-bearing and female- 

 bearing eggs in equal numbers ; all males are homozygotes, 

 carrying only maleness, and producing only male-bearing 

 spermatozoa.' This theory was supported by the remarkable 

 researches detailed by Miss Stevens, through which Professor 

 E. B. Wilson, herself, and other American cytologists have 

 demonstrated the presence of an odd number of chromosomes 

 (one less than the normal number) in some spermatozoa of 

 ■certain species of insects, these spermatoza apparently fertilising 

 female-bearing eggs, those with the full number male-bearing 

 eggs. Professor Bateson also supported the theory from 

 breeding experiments with Canary Finches. Mr. Heape, on 

 the other hand, gave reasons — derived for the most part from 

 human birth-statistics — in support of somatic influence on the 

 determination of sex. 



Evolutionary problems of an older and simpler type were 

 raised on Thursday, 3rd, by Professor Poulton, Dr. F. A. 

 Dixey, and Mr. J. C. Moulton, who exhibited and discussed 

 series of butterflies, illustrating ' convergent mimicry ' of 

 distasteful forms. Embryologists were well pleased to wel-^ 

 •come Professor A. W. Hubrecht as a vice-president ; he 

 took the chair on Monday afternoon, September 7th, when 

 Professor J. P. Hill described the ' Segmentation of the Mar- 

 supial Ovum,' and Professor E. W. MacBride ' Gastrulation 

 in Amphioxus.' These two authors defended respectively 

 the ancestral value of the monotreme yolked egg, and the 

 ectodermal nature of all the inpushed cells in the Amphioxus 

 gastrula. Both of these familiar positions were genially 

 attacked by the great Dutch embryologist. Later in the same 

 afternoon, Dr. A. Smith Woodward, F.R.S., of the British 

 Museum, delighted the Section with a lecture on the ' Evolu- 

 tion of Fishes.' On Friday afternoon (4th Sept.), Prof. Cossar 

 Ewart lectured on the ' Wild Ancestors of the Domestic Horse,' 



Geographical zoology was represented hy Dr. W. A. Cun- 



1908 December i. 



