192 



PHYSICAL BASIS OF HEREDITY 



race with pale caterpillars. One of these was banded on the 

 left side (which side was also female) and pale on the right 

 side (which was also male). The sex of the two sides was 

 only apparent after the moth had appeared. The banded 

 character of the worm is kno^^^n to be dominant to the pale 

 character, but neither is sex-linked. The case can be 

 explained, if as the evidence indicates, the mother was 



<ft^i:> 



^V^ 



rc t) 





-M 





'%pri 



striped 



gynandromorph 



plain 



Fig. 89. — Caterpillars of the silkworm moth. A striped one to the left, a plain one to 

 the right, a hybrid gynandromorph in the middle. 



heterozygous for a not sex-linked character, banded, and 

 if she produced an egg with two nuclei (Fig. 90). Don- 

 caster has found such eggs in Abraxas, and has shown 

 that each nucleus extrudes separately polar bodies, and 

 that each reduced egg nucleus is fertilized by a separate 

 spermatozoon. If as shown in the next diagram one 

 reduced nucleus has a TF-chromosome, and a factor for 

 banded carried in one of the autosomes, and the other 

 reduced nucleus has a Z-chromosome, and in one of the 



