64 BIOLOGY AND SOCIAL PROBLEMS 



and these are usually produced by different 

 individuals. Individuals that produce sperm 

 cells are called males, those that produce egg 

 cells, females. The production of a new indi- 

 vidual is initiated as a rule by the fusion of 

 a sperm cell from one individual with an egg 

 cell from another. For obvious reasons this 

 method of reproduction is designated as sex- 

 ual in contrast with non-sexual reproduction, 

 which is the term used for the simpler type. 



Sexual reproduction is the common method 

 of increase among the multicellular animals, 

 especially the more complex forms, but it can- 

 not be said to be entirely absent from the 

 unicellular organisms. In man reproduction is 

 accomplished almost exclusively by the sexual 

 method, there being only a few somewhat ob- 

 scure and rare occurrences that can be inter- 

 preted otherwise. 



When we reflect on the enormous struc- 

 tural complexity of the human body, its count- 

 less myriads of cells appropriately disposed to 

 form its organs, and particularly when we 

 attempt to realize the immense variety of proc- 

 esses which go on within it, many of which 

 are essential to its continuance, it seems as 

 though a reproduction of such a complex 



