GERM CELLS OF GRYLLOTALPA 301 



admit crossing over. To Carothers the chromosome is a unit 

 and she believes all the facts of Mendelian heredity can be 

 explained without assuming an interchange of factors at synapsis. 

 She does not discuss experimental results which demonstrate 

 crossing over. Carothers, however, does not meet smooth sail- 

 ing everywhere. She has not examined the female cells, but 

 of course has to assume that there is an unequal pair of chromo- 

 somes present and that, in maturation, either the small or the 

 large end of the unequal pair may remain in the egg. As all 

 the males have the unequal pair, she has to further assume 

 that a spermatozoon with the large chromosome can fertilize 

 only an egg with the small chromosome and vice versa. So far 

 as I know, we have no direct evidence of selective fertilization, 

 and I am not quite willing to admit it without such evidence. 

 Further, Robertson ('15), who has described a similar unequal 

 pair of chromosomes in several species of grasshoppers, does 

 not find the unequal pair in all males, and he thinks Carothers 

 may find this to be the case upon further study. He is not 

 forced to assume selective fertilization. 2 



2. MITOCHONDRIA 



My material was prepared for a study of the chromosomes. 

 As that fixed in Fleming and stained with iron haematoxylin 

 showed the mitochondria with particular clearness, it seemed 

 worth while to describe them, especially so since there is still 

 need for work in this field. Despite the fact that a large amount 

 of work has been done, particularly by Europeans, conflicting 

 views exist as to the origin, function, and fate of these bodies. 



A. In the male sex cells 



The spermatogonial cells are arranged in the form of a rosette 

 (plate 1, A). Due to this arrangement, the inner ends of the 



2 In regard to sex inheritance I have nothing new to add, but I wish to correct 

 a statement in my former paper ('12). I stated that Wilson had practically 

 abandoned the quantitative theory of sex production. Wilson informs me that 

 such is not the case and I wish to express my regrets for misquoting him. The 

 error was due to misinterpreting a paragraph in his paper of 1911. 



