REPRODUCTION. 



843 



the eighteenth and part of the nineteenth centuries, we find among 

 investigators and interpreters of this phenomenon two extreme views 

 represented. Some investigators considered the spermatozoon as a 

 very minute but complete animal ammalculus containing all the 

 organs of its parent animal en miniature. By means of a slender 

 tail they were supposed to move around until they found an appro- 

 priate soil the ovum to which they became attached and from 

 which they received the necessary stimulus to grow, and gradually 

 attained the size characteristic to the type. The advocates of this 

 view have been known as animalculists. 



The advocates of the other, extremely oppo- 

 site, view the ovists considered the ovum to be 

 like the bud of the plant, containing all the parts 

 of the future animal wrapped together, and, being 

 met by the spermatozoon, the parts received a 

 stimulus for their unfolding and growth until the 

 typical size has been reached. It is obvious that 

 these both extreme views are based on a common 

 supposition that either the spermatozoon or the 

 ovum represents an already preformed organism, 

 and therefore both of these views have accord- 

 ingly been known as the theory of preformation. 

 A detailed account of other theories on this sub- 

 ject is generally given in text-books of embry- 

 ology. For the understanding of the physiology 

 of reproduction, it suffices to state that subsequent Fig. 379. Human 

 investigations have proven conclusively that Spermatozoon, 

 the ovum as well as the spermatozoon repre- (MANTON.) 

 sent but single cells. Simultaneously with the astonishing facts, 

 revealed during the last few decades, of the structure and life-his- 

 tory of the cell in general, which are presented in the first chapter 

 of this book, very much light has been thrown on the structure and 

 life-history of the cellular elements specialized for reproduction. 

 According to the facts known at the present time, it is pretty well 

 established that both the spermatozoon and the ovum originate from 

 the same source, the germinal epithelium; both undergo a prelim- 

 inary process of ripening, maturation, before they are able to par- 

 ticipate in fertilization; and, while the role assigned to one of them 

 in the latter process is not exactly the same as the role assigned to 

 the other, they are nevertheless equivalents in regard to their ultimate 

 significance for the process of producing a new individual. 



