IIO THE EVOLUTION OF SEX. 



SUMMARY. 



I. The contrast between the elements is that between the sexes. The 

 large, passive, highly-nourished anabolic ovum ; the small, active, katabolic 

 sperm. 



II. Hamman's discovery, 1677 ; Leeuwenhoek's interpretation ; the school 

 of animalculists ; Kolliker's demonstration of the cellular origin of the sperm, 

 1 841. 



III. Structure of the sperm, — nuclear "head" of chromatin, protoplasmic 

 "tail," middle portion. The sperm in reality comparable to a monad or 

 flagellate infusorian, only with less cell substance. Its occasional degreda- 

 tion into the amoeboid phase. 



IV. Physiology of the sperm ; its locomotor energy at a maximum, but 

 yet great power of endurance, like a monad or bacillus. 



V. Origin of sperms from the division of a mother-sperm-cell homologous 

 with the ovum. The different modes of "spermatogenesis" may be collated 

 with the different modes of ovum-segmentation. 



VI. The occurrence in sperm-development of phenomena comparable both 

 structurally and functionally with polar globula formation. 



VII. Chemistry of the sperm ; resemblance between pollen and sperma- 

 tozoa. 



LITERATURE. 



Geddes, P., and Thomson, J. A.— History and Theory of Spermatogenesis. 

 Proc. Roy. Soc. Edin., 1886, pp. 823-S24, 1 pi. See "also Zoological 

 Record from 1886. 



