Il6 THE EVOLUTION OF SEX. 



SUMMARY. 



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

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

 sperm. 



2. Hamm's discover}", 1677 ; Leeuwenhoek's interpretation ; the school 

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

 sperm, 1S41. 



3. 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 degra- 

 dation into the amoeboid phase. 



4. Physiology of the sperm ; its locomotor energ}- at a maximum, but 

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



5. Origin of sperms from the division of a mother-sperm-celi 

 homologous with the ovum. The different modes of "spermatogenesis'' 

 may be collated with the different modes of ovum-segmentation. 



6. The occurrence in sperm-development of phenomena comparable 

 both structurally and functionally with polar-globule formation. 



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

 tozoa. 



LITERATURE. 



Geddes, p., and Thomson, J. A. — Histor)' and Theory of Spermato- 

 genesis. Proc. Roy. Soc. Edin., 1886, pp. 803-823, i pi. See also 



Zoological Record from 1886. 



