THE GERM-CELLS OF CICADA (TIBICEN) SEPTEMDECIM. 429 



tion of the spermatid into the spermatozoon. O. Vander Stricht 

 calls the Nebenkern of the spermatid a "vitelline body." Wild- 

 man ('14) ascribes a nutritive function to the mitochondria 

 (karyochondria) of the spermatid of Ascaris. The view has 

 often been expressed that the mitochondria of the spermatozoon 

 are concerned in locomotion, since they usually form a part of 

 the tail. On the basis of the behavior of the mitochondria in 

 spermatogenesis, we can only say that, just like the acrosome or 

 the axial filament, they form a definite structural element of the 

 spermatozoon, and it may be that their only significance is 

 bound up with their function as an organelle of the spermatozoon. 

 This view is contested by Meves, Duesberg and others on the 

 basis of their observations on fertilization in certain forms where 

 the mitochondria of the sperm apparently enter the egg and can 

 be traced into the cleavage cells. If this behavior of the mito- 

 chondria can be found to be of general occurrence in fertilization, 

 their significance from the point of view of heredity and develop- 

 ment becomes of utmost importance. It may be said that the 

 evidence for this is still in a very unsatisfactory state. I shall 

 reserve for later discussion the questions bearing on this problem, 

 until added observations on the mitochondria during oogenesis 

 may be presented. 



2. Nutrition of the Egg. 



Without entering into a detailed description of the structure 

 of the ovary of Cicada, I wish merely to mention some facts in 

 regard to the nutrition of the egg during the growth period. The 

 study of insect ovaries dates back over a century, many of the 

 works being concerned with the question of the origin of the 

 various cell-elements, viz., germ-cells, nurse-cells, epithelial cells 

 and follicle-cells. Much of this work is of little value for the 

 solution of these problems, since the study has been usually 

 confined to that of the adult ovaries, and it is evident that only 

 an embryological as well as a histological study of the ovary can 

 enable us to come to any definite decisions. As pointed out by 

 Hegner ('14), the origin of the nurse-cells and germ-cells may be 

 different in different forms. In the case of Miastor, Hegner states 

 that the nurse-cells are mesodermal in origin, while in the 

 Chrysomelid beetles "the nurse-cells in the ovaries seem to be 



