2 Chromosomes and Sex hi Abraxiis 



of 1912 had accidentally been made up by my assistant to only one- 

 tenth of the normal strength, and on making up the correct solution 

 it gave very inferior results. Tap-water gave the best results of all. 

 Sections for both ovarian and maturation divisions were stained with 

 Heidenhain's Iron Haematoxylin ; in the latter case the stain nmst 

 be washed out until the yolk is left almost colourless. 



For the maturation of the eggs, I have to thank Miss P. H. Dederer 

 of New York for giving me full information in writing about the 

 methods used by her in studying the maturation divisions of Philo- 

 samia cynthia. I followed her methods in general, with modifications 

 due to the much smaller eggs and thinner shells of Abraxas grossu- 

 lariata. The eggs were fixed at varying times up to about 3 hours 

 in Carnoy's alcohol sublimate (absolute alcohol, glacial acetic acid, 

 chloroform, in equal parts ; sublimate to saturation). They were then 

 washed in 70 % alcohol, and usually treated with iodine in 70 or 90 % 

 alcohol to remove the sublimate, and preserved in 80 J^ alcohol. For 

 cutting sections it is necessary to remove the shell, always a trouble- 

 some and often a difficult operation. In some batches the egg is 

 contracted away from the shell, and the shell can then be removed 

 without much difficulty with needles under a binocular dissecting 

 microscope. In some cases, eggs which had been treated with iodine 

 seemed to have softer shells, but I am not sure that this is general. 

 The removal of the shell seemed usually to be considerably e;isier in 

 eggs which had been kept for some weeks in spirit. In other liatches 

 the protoplasmic layer of the egg sticks to the shell, and to remove 

 it without tearing it from the yolk is a matter of gi-eat difficulty. If it 

 is once separated from the yolk, accurate orientation becomes impossible 

 and the polar region often cannot be found in the .sections. The polar 

 spindles are at the anterior end of the egg, w'hich in this species can 

 generally be recognised by the less marked sculpturing of the shell. 

 The shell was pricked and torn apart from the posterior end when this 

 could be identified. The shelled eggs were passed through absolute 

 alcohol into cedar oil for some hours or more, placed in xylol for a few 

 minutes, and embedded in paraffin melting at 60'. The sections were 

 cut transversely as a rule, with a thickness of 10 /i. 

 a. Breeding Eivperiinents. 



The main facts established in the previous paper were that in a 

 certain strain families appeared in each generation consisting entirely 

 of females ; some of these females again have only female offspring, 

 while others, apparently of about equal number, produce males and 



