30 EXPERIMENTAL EVOLUTION LECT. 



of a Pascal, a Lavoisier, a Newton, a Goethe, a Shake- 

 speare, a Pasteur, or a Darwin, becomes to the natur- 

 alist a subject of meditation still more extraordinary 

 and astounding. This form of evolution is to be seen 

 in all organisms, save in the simpler ones where no 

 process of reproduction is present except mere division, 

 and where the organism consists of mere cells one or 

 more without any specialized organs and functions. 

 There is a striking sameness in the development 

 of animals of the same group, however much they 

 may differ from each other when they attain the 

 adult form. Such is the case, for instance, with many 

 parasitic crustaceans. While the adult Sacculina, for 

 example, is a mere mass of suctorial appendages 

 converging towards an alimentary canal, and presents 

 not a single one of the external characters of any 

 adult crustacean, development shows the character- 

 istic form of the crustacean larva, and no doubt can be 

 felt as to the real nature, affinities, and systematic 

 position of the degenerate adult, however unlike the 

 general crustacean type it may be. 



This individual evolution is named ontogeny, as all 

 know, and evolutionary naturalists consider it as repeat- 

 ing, under a condensed and abridged form, the evolution 

 of the species, or group, that is to say the pJiylogeny 

 or palaeontological evolution. And while the study of 

 the transitional phases in individual evolution shows 



