Germ Cells of Leptinotarsa Signaticollis. 175 



nutrition. The same principle can be applied in the case of the 

 nurse cells. When the latter are being differentiated for their 

 specialized function, very rapid and prolonged amitotic divisions 

 occur. In degenerating cells amitosis is to be expected, because 

 in many cases at least, the cells or tissues do not receive their nor- 

 mal oxygen supply. 



Amitosis in the higher forms as a survival of a primitive process 

 of direct division from the protozoa was suggested long ago by 

 Strassburger ('82) and Waldeyer ('88), but the view has never met 

 with much favor. This has been largely because of the popular 

 and growing tendency since that time to associate amitosis with 

 processes of degeneration and specialization, reserving for mitosis 

 exclusively the role of cell multiplication in normal processes. 

 However, there is much to support the older view, and the 

 evolution of the mitotic method of cell division is, in a way, the 

 expression of the evolution of a higher type of cell metabolism 

 than that found in the lower forms. The raison d' etre of the 

 mitotic figure must rest upon a physiological basis, and the 

 complexity of the mitotic cycle appears to be associated with a 

 corresponding complexity of metabolism of a higher order than 

 that found in cells that divide amitotically. In this sense ami- 

 tosis in the germ cells of the testis and ovary of Leptinotarsa can 

 be regarded as a temporary reversion to an ancestral method of 

 division but the direct cause I believe, lies in some disturbance 

 in the cell metabolism which occurs periodically in the ontogeny. 



The appearance of the amitotis division figure is by no means 

 the same in all cases, and this is of importance from the phyletic 

 stand point. In nearly every instance, the process indicates a 

 division of the nucleus into two approximately equal parts,but 

 among the germ cells the mechanism is more carefully adjusted 

 for this purpose (cf. figs. 21, 22, 23, 34, 35, 68, 69, etc.) Thus in the 

 ovogonia and spermatogonia division of the nucleus is preceded 

 by a very exact division of a large chromatin nucleolus, and as 

 the halves separate surrounded by the clear area, the appearance 

 reminds one very much of the division of a chromosome on a 

 spindle. In fact, the process suggests a very primitive method 

 of karyokinesis. Meves ('91) and Benda ('93), in Salamadra 



