Il8 AMPHIMIXIS OR ESSENTIAL MEANING OF [XII. 



proved, as might have been expected, that this difference in the 

 number of loops in the youngest germ-cells exists also in the 

 male sex. He called the variety w^hich produces two loops 

 Var. univalens, and that which produces four Var. bivalens. Since 

 the development of the spermatozoa in both varieties differs 

 only in the number of nuclear loops which are formed, I will, 



KedU 



Fig. I. 



Formation of spermatozoa in Ascm-is inegalocephala, var. bivalens (modi- 

 fied from O. Hertwig). A. Primitive sperm-cells. B. Sperm-mother-cells. 

 C. First 'reducing division.' D. The two daughter-cells. E. Second 

 ' reducing division.' F. The four grand-daughter cells, — the sperm-cells. 



in the following account, deal with only one of them, the Var. 

 bivalens. 



The formation of the spermatozoa falls into three stages ; the 

 first is that of the ' primitive sperm-cells ' : these youngest male 

 germ-cells then proceed to increase by means of successive 

 divisions. The division of the nucleus is effected by kar3'^okinesis 

 after the usual manner ; the four nuclear loops split longitudinally 

 and the halves form the two daughter-nuclei. After this process 



