568 Theophilus s. Painter, 



Maevia vittata, the ctetosomes commend themselves to us, rather than 

 the planosomes, for two reasons. First, because the ctetosomes show 

 a definite mode of distribution, while the planosoraes are very irre- 

 gularly distributed to the spermatids and follow no law but that 

 of chance. Second, I have found that the ctetosomes. when present, 

 are present in a definite number in all of the males while the plano- 

 somes vary within wide limits. It seems improbable that the latter 

 bodies have any influence in heredity, since they may be present in 

 large numbers or absent from the germ cells without influencing the 

 somatic characters. 



For these reasons we have discarded the planosomes as far as any 

 hereditary significance is concerned, and it is safe to say that if 

 the basis of this dimorphism is to be found in the chromosomes, we 

 must look to the ctetosomes for the determining causes. 



It is realized that, because a body is present in one variety 

 and absent from the other, is no proof that it has to do with the in- 

 heritance of certain external characters. This could only be deter- 

 mined by breeding. But if we assume that the presence of the cteto- 

 somes gives us the gray male while the absence of these bodies 

 gives us the tufted males, from a cytological standpoint, the inheri- 

 tance of these characters would be as follows. A glance at Dia- 

 gram I, will show that the sperm of the gray variety is of three 

 kinds: a) Sperm which carry the accessory chromosomes and the 

 ctetosomes. b) Sperm which carry only the accessory chromosome. 

 c) Sperm which carry neither of these elements. 



Since the female carries two measures of the accessory chromo- 

 some, it follows that the sperm which carry the accessory elements, 

 will be the female producing sperm, while the sperm which does not 

 carry the accessory chromosome will be the male producing sperm. 

 In other words, the temale will determine the hétérochromosome 

 condition of the male. Since the males are different with regard 

 to the presence or absence of the ctetosomes, it follows that the 

 mature eggs must be of two kinds: 



a) Eggs which carry the accessory chromosome and the cteto- 

 somes. 



h) Eggs which carry only the accessory chromosome. 



A glance at Diagram III will make this clear. 



On the assumption that the ctetosomes produce the gray variety 

 while the absence of these bodies gives a tufted male, the inheritance 

 of these characters is very simple. And although, in a constantly 



