Germ Cells of Leptinotarsa Signaticollis. 173 



described amitotic cell division in the stellate cells of the body 

 mesenchyme. Like Patterson and Child, he believes it occurs in 

 regions of rapid cell proliferation, and attributes to it a normal 

 physiological significance of some kind. 



The occurrence of amitosis in so many different forms and such 

 a variety of circumstances makes it imperative that this type of 

 cell division be recognized as a factor in normal developmental 

 processes. In view of so many accounts, only a few of which are 

 mentioned above, the fact of its existence must be generally 

 recognized, but the question of its significance and relation to 

 mitosis remains without a satisfactory answer. 



In the species under consideration, I have described two distinct 

 types of amitosis. In the case of the nurse cells, the process is 

 evidently concerned with the differentiation of these cells for a 

 highly specialized function. Mitosis never occurs afterward. 

 The existence of the direct form of cell division under these ct)n- 

 ditions has been accepted without much question since it was 

 regarded as a species of degeneration, and further, was in no wise 

 antagonistic to the hypothesis of the individuality and continuity 

 of the chromosomes. In other cases where the claim has been 

 made that mitosis may follow amitosis, so long as only somatic tis- 

 sue was involved, no very serious objections have been made. 

 However, when we come to instances of amitosis among the germ 

 cells that later develop into functional reproductive cells, the sup- 

 porters of the chromosome hypothesis have found it very difficult 

 to accept the results of such observations. 



Bearing in mind the theoretical interest centering about this 

 point, I have been very careful to examine the ground thoroughly 

 before stating definitely the occurrence of amitosis in the germ 

 cells of Leptinotarsa. I have already pointed out that it is merely 

 transient and inconspicuous in the ovogonia. In the spermato- 

 gonia it is more prominent, persists longer and is involved in the 

 formation of the cysts. 



The experiments of Gerassimow ('92), Nathansohn ('00), and 

 Haecker ('00), have suggested to me that disturbances in the nutri- 

 tion may be responsible for the amitotic period; the effect of 

 narcotics and low temperature being similar to what one migh*: 



