;. 



64 FACTS AND FANCIES 



ing," a rudimentary backbone, and enables us 

 at once to recognize in the young ascidian an 

 embryo man. 



A second method characteristic of the book, 

 and furnishing, indeed, the main basis of its ar- 

 gument, is that of considering analogous pro- 

 cesses as identical, without regard to the differ- 

 ence of the conditions under which they may be 

 carried on» The great leading use of this argu- 

 ment is in inducing us to regard the develop- 

 ment of the individual animal as the precise 

 equivalent of the series of changes by which 

 the species was developed in the course of ge- 

 ological time. These two kinds of develop- 

 ment are distinguished by appropriate names. 

 Ontogenesis is the embryonic development of 

 the individual animal, and is, of course, a short 

 process, depending on the production of a germ 

 by a parent animal or parent pair, and the fur- 

 ther growth of this germ in connection more or 

 less with the parent or with provision made by 

 it. This s, of course, a fact open to observa- 

 tion and study, though some of its processes 

 are mysterious and yet involved in doubt and 

 uncertainty. Phylogenesis is the supposed de- 

 velopment of a species in the course of geo- 

 logical time and by the intervention of long 



