in the Animal Kingdom. 137 



tion tends to embarrass, but the history of development, at that 

 period when structure presents itself alone ; and, as Von Bar has 

 justly said, this will perhaps " one day become the ground 

 for nomenclature," * as it can be the only one on which to form 

 a correct estimate of parts, in different animal forms. 



Certain elements, proceeding from the elements of an indivi- 

 dual, or from the elements of two individuals, constitute, by a 

 separate or distinct existence, another individual, a germ ; des- 

 tined, like its parent or parents, to undergo, by a succession of 

 elements, continued changes in its component parts ; and, by 

 degrees, to attain a state of being, represented by a form, be- 

 longing to the parent-type. 



These elements, while they constituted part of the parent or 

 parents, shared the state of being, peculiar to the latter. It is 

 then easily conceivable, that, having themselves acquired a sepa- 

 rate or distinct existence, the new being they constitute, should 

 contain within itself, properties analogous to those of its parent 

 or parents ; and that therefore, in its progress towards its des- 

 tined state of being, it should undergo similar changes ; that it 

 should attain the parent-type, and also more or less of individual 

 resemblance to its parent or parents. 



The elements of every germ must have innate susceptibi- 

 lities of a certain definite arrangement ; so that, on the applica- 

 tion of stimuli, there results a certain structure.-)- These we 

 shall in future call, innate susceptibilities of structure, or in- 

 nate (plastic) properties. All innate properties are of course de- 

 rived from the parent or parents. If the germ be animal, its 

 leading properties are those characterizing animals in general. 

 But it has others, common respectively to the class, order, fa- 

 mily, genus, species, variety, and sex, to which the germ be- 

 longs. Lastly, it has properties that were previously charac- 

 teristic of its parent or parents ; in which, indeed, all the others 

 are included. But no innate properties, except those merely 

 animal, are at first, to our senses at least, apparent in the struc- 

 ture of the germ. 



The sum of these innate (plastic) properties, determines the 



1. c. p. 233. 



t The stimuli are those circumstances that produce development ; such as 

 nourishment, a peculiar ambient medium, and a certain degree of warmth. 



