2GG ESSAY ON CLASSIFICATION. 



characterized by relations and proportions of parts among 

 themselves, and of the individuals to one another and 

 to the surrounding mediums ; we finally reach indi- 

 viduals, which, for the time being, represent not only the 

 species with all their varieties, and variations of age, sex, 

 size, etc., but also the characteristic features of all the 

 higher groups. We have thus, at one end of the series, 

 the most comprehensive categories of the structure of 

 animals, while at the other end we meet individual beings. 

 Individuality on one side, the most extensive divisions of 

 the animal kingdom on the other. Now, to begin our 

 critical examination of the progress of life in its successive 

 manifestations with the extremes, is it not plain, from all 

 we know of Embryology, that individuahzation is the 

 first requirement of all reproduction and multiplication ; 

 and that an individual germ, (or a number of them,) an 

 ovarian egg, or a bud, is first formed and becomes distinct 

 as an individual from the body of the parent, before it 

 assumes either the characters of its branch or those of its 

 class, order, etc. \ This fact is of great significance as 

 showing the importance of individuality in nature. Next, 

 it is true we generally perceive the outlines of the plan 

 of structure before it becomes apparent in what manner 

 that plan is to be carried out ; and the character of the 

 branch is marked out, in its most general features, before 

 that of the class can be recognized with any degree of 

 precision. Upon this fact, we may base one of the most 

 important generalizations in Embryology. 



It has been maintained, in the most general terms, 

 that the higher animals pass during their development 

 through all the phases characteristic of the inferior classes. 

 Put in this form, no statement can be further from the 

 truth ; and yet there are decided relations, within certain 



