296 



THE BEGINNINGS OF LIFE. 



never seen a preliminary coupling of two individuals. 

 In specimens of the genus Kerona he has occasionally 

 observed this coupling, though he has never seen more 

 than a single germ. The nature of the body in these 

 animals was rendered even more indubitable by the fact 

 that it became converted into an embryo whilst still 

 within the posterior part of the body of the parent. 

 His observations were principally conducted upon spe- 

 cimens of Kerona lepus measuring -^' in diameter 

 and in which the germ (here again free within the body) 



was about 



1 " 



in diameter. M 



tion of the embryo, and the characteristic contractile 

 vesicle make its appearance, so as to leave no doubt 

 that the process of development was still advancing \ 

 Multiplication by the ordinary processes of repro- 



p 



' This production of embryos in the substance of dying Infusoria is 



a subject of much interest. To me it was a matter of special interest to 



read (in 1869) M. Pouchet's description after I had already, as 'a result 



of frequent careful observation, come to the conclusion that the nucleus 



of the white blood corpuscle was also evolved during the later stages 



of Its life within its very substance ; and that it was destined to come to 



maturity and perhaps, under certain circumstances, take the form of a 



distinct anatomical element, whilst the rest of the parent structure was 



about to undergo a process of disintegration (see vol. i. p. 227). This 



process seems to be most comparable with that by which the embryo 



is evolved within the body of the Infusorial animalcule. Here also the 



germ (nucleus) is evolved out of the substance of the parent organism 



itself, at a time when its own vitality is about to cease. As a sort of 



Imk connecting these two sets of phenomena, we may perhaps refer to the 



development of the moving illaments known as Spermatozoa from the 



nucleus of the sperm cell. The old element dies in giving birth to the 



new product ; and the new element in this case is an actively-moving. 



independent zooid. - - — . 



1^' 



W 



111 



T 



■J , 



i .f -D 



-im 0' 



in. in the ^ 



) 



,...,1 tuiu " **. w 



zi \m of inf 



-■;, concermng 

 ■y of reprod 



uc 



■i-tcomparativ( 

 ■' " \ fission 



c 



>^. ' 



( 



( 



1. 



•A', 



'\--i^^on$ of 





"L 



'> Of , 



reojj 





pnr 



\v 



