154 



THE DEVELOPMENT OF THE GAMETES OR SEX CELLS 



are numerous, there is a strong tendency for spermiogenesis to follow similar 

 lines of development. Deviations occur, but the following comparisons between 

 mammalian and insect spermiogenesis, somewhat modified from Bowen ('22), 

 illustrate the uniformity of transformation of the basic structures of the 

 primitive meiocyte: 



Mammalian Sperm 



Insect Sperm 



Nucleus — head 



Centrioles — originally double and ar- 

 ranged in a proximal-distal formation. 

 The axial filament arises from both 

 centrioles 



Mitochondria — form an elaborate sheath 

 for the anterior portion of the axial 

 filament 



Idiosome and Golgi apparatus (acroblast 

 portion) — gives origin to a vesicle 

 which contains a granule, the acrosome 

 granule, which is involved in the pro- 

 duction of the acrosome 



Excess Golgi substance — cast off with 

 excess cytoplasm 



Excess cytoplasm — cast off — may be part 

 of seminal fluid or possibly may be 

 engulfed by Sertoli cells 



Nucleus — head 



Centrioles — same as in mammals 



Mitochondria — form a somewhat 

 similar sheath for the axial fila- 

 ment 



Idiosome and Golgi apparatus — 

 much the same as in mammals 



Excess Golgi substance — cast off 

 with excess cytoplasm 



Excess cytoplasm — cast off — may be 

 part of seminal fluid or possibly 

 may be engulfed by epithelial cells 

 of the sperm cyst wall 



c. Cytoplasmic Differentiation of the Egg 

 The cytoplasmic differentiation of the egg involves many problems. These 

 problems may be classified under three general headings, viz.: 



( 1 ) Formation of the deutoplasm composed of fats, carbohydrates and 

 proteins, 



(2) development of the invisible organization within the true protoplasm 

 or hyaloplasm, and finally, 



(3) formation of the vitelline or egg membrane or membranes. 



In view of the complexity of these three problems and of their importance 

 to the egg in the development of the new individual, the mature oocyte or 

 egg is in a sense no longer a single cell. Rather, it is a differentiated mass 

 of protoplasm which is capable, after proper stimulation, to give origin to 

 a new individual composed of many billions of cells. As such, the differen- 

 tiation of the oocyte within the ovary represents a relatively unknown period 

 of embryological development. 



