GERM CELLS OF GRYLLOTALPA 299 



tion no exception to the other sex chromosome combinations. 

 That is, when viewed from a broad comparative standpoint, the 

 group seems to be one similar to that in Conorhinus, Fitchia, 

 and Thyanta, with the exception that here the grouping occurs 

 in the first division instead of the second, and that the two 

 chromosomes which go to the female-producing pole have lost 

 the intimate association which they have in the other forms. 

 If we consider Gryllotalpa as an isolated case, the evidence is 

 certainly in favor of the interpretation that we have here an 

 unequal pair of idiochromosomes and an odd chromosome. The 

 behavior of the single unpaired chromosome is typical of that of 

 an accessory. It passes undivided in the first maturation divi- 

 sion to one pole and divides in the second. The class of sper- 

 matozoa which receives it is the female-producing class, the other 

 the male-producing. The behavior of the unequal pair is typical 

 of the behavior of a pair of idiochromosomes. In the first divi- 

 sion the two components pair to form an unequal bivalent, the 

 two parts of which separate, the large end passing to one pole, 

 the small end to the other. Both parts divide in the second. 

 Of the two classes of spermatozoa thus produced, the one which 

 receives the large end is female-producing, the one which receives 

 the small end, male-producing. The only thing which indi- 

 cates a relationship between the unequal pair and the single 

 chromosome is the fact that the large end of the unequal pair 

 and the single chromosome always pass to the same pole of the 

 spindle in the first division. However, they are not intimately 

 associated, as in Conorhinus and others, but pass separately and 

 independently to the same pole. It is only from the compara- 

 tive standpoint then that the second interpretation seems the 

 more plausible. 



In the preliminary paper, I also discussed briefly the arrange- 

 ment and movement of the chromosomes on the spindle. It has 

 been assumed that this arrangement is a matter of chance, an 

 assumption made in order to explain Mendelian heredity. Until 

 recently we had no direct evidence for or against such an assump- 

 tion although it was generally accepted. I wish to state that I 

 myself accept the theory and in the light of recent evidence 



