Volume II NOVEMBER, 1912 No. 3 



THE CHROMOSOMES IN THE OOGENESIS AND 

 SPERMATOGENESIS OF PIERIS BRASSICAE, 

 AND IN THE OOGENESIS OF ABRAXAS 

 GROSSULARIATA. 



By L. DONCASTER, M.A.. 

 Fellow of King's College, Cambridge. 



In a recent note^ on some stages in the spermatogenesis of Abraxas 

 grossulariata I showed that there is apparently no inequality in the 

 chromosomes of the spermatocyte divisions, corresponding with the 

 hetei'ochromosomes which have been found in other orders of insects. 

 The same result has been found by others in Lepidoptera. I know, 

 however, of no careful study of the oogenesis in this order, and since 

 in Abraxas the sex-limited character is transmitted by the female only 

 to her male offspring, it seemed possible that there might be inequality 

 in the chromosomes of the eggs, corresponding with the male-deter- 

 mining and female-determining eggs, which are shown to exist by the 

 facts of sex-limited inheritance. In Abraxas the chromosome number 

 is large (the reduced number being 28), and in my first attempts to 

 investigate the subject I failed to find oogonial mitotic figures which 

 were suitable for accurate observation. On searching for other Lepi- 

 doptera which might provide more suitable material, I found that the 

 Large White Butterfly {Pieris brassicae) has a much smaller number 

 of chromosomes, with clearer mitotic figures. After following out the 

 available stages in Pieris, the experience so gained, and especially 

 the fact, unknown to me in my earlier attempts with Abraxas, that the 

 oogonial divisions take place chiefly in the larva, enabled me to return 

 to the study of Abraxas with more success, and to work out the 

 earlier stages of oogenesis with some completeness. In the following 



' Journal of Genetics, Vol. i. p. 179. 

 Joam. of Gen. ii 14 



