PART III 



REPRODUCTION AND DEVELOPMENT 



CHAPTER XXVII 

 REPRODUCTION 



The first living beings must have originated by spontaneous 

 generation (generatio sequivoca), i.e. the origination of living 

 beings from lifeless material. At present, spontaneous generation, 

 so far as we know, does not occur, and new living beings originate 

 by biogenesis, i.e. the formation of living beings from separated 

 parts of previously existing living beings. 



Reproduction may be : 



(a) Asexual (reproduction by fission, budding, spore forma- 

 tion). In this, one separated portion of a living being develops into 

 a new individual. 



(b) Sexual reproduction, in which two sexually different cells 

 (egg and sperm cell) unite and develop into a new living being. 

 These two sexual cells may either originate from one individual or 

 from two sexually different individuals (male and female). 



Human beings are propagated by sexual reproduction in 

 which the egg-cell provided by the ferrfale unites with the 

 sperm-cell furnished by the male and from this a new indi- 

 vidual develops. 



1. THE MALE SEX-PRODUCTS AND THEIR FORMA- 

 TION 



i . Composition of the seminal fluid. The seminal fluid 

 is a viscid, whitish, turbid fluid having a peculiar odor and 

 a neutral or alkaline reaction in which are suspended the 



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