194 THE BEGINNINGS OF LIFE. 



is similar in kind although necessarily larger than its 

 components. 



Similar mutual attractions, however, may be exerted 

 by other living units when brought into close contact 

 with one another, and the result may be the forma- 

 tion of an aggregate in which considerable molecular 

 changes are compelled to take place. The products 

 resulting from such a fusion may be quite different 

 from the originally fused units j whilst they will differ 

 at different times according to the precise nature and 

 number of the units which enter into combination. 

 Such processes are frequently to be observed taking 

 place in various parts of the ^ proligerous pellicle.' It is 

 in this way, in fact, that those phenomena occur which 

 make the name <^ proligerous pellicle' suitable for the scum 

 that forms on organic infusions. The processes them- 

 selves come under the head of Heterogenetic Biocrasis. 



The first person who actually described the micro- 

 scopical appearances characterizing the evolution of 

 higher organisms from the pellicle, was M. Pineau. 

 This he did in 1845, in a memoir entitled, 'Recherches 

 sur le Developpement des Animalcules Infusoires et des 

 Moisissures ^' More precision, however, was given to 

 the subject in 1859, by M. Pouchet, when he described 

 in his ' Heterogenie,' the mode of origin of some of 

 the organisms which had formed the objects of Pineau's 

 investigations, as well as of some different organismis. 



1 See 'Ann. des Sc. Nat.' (Zoologie), t. iii. p. 182, and t. iv, p. 103. 



