in the Animal Kingdom. 



individual structure ; and tfwp^r-fcetation may be, in part at least, 

 the cause why this is not always the case.* 



The innate (plastic) properties include, as already said, some 

 that are characteristic of animals generally, and others common 

 to all the animals contained in that division of the animal king, 

 dom, to which the species is subordinate. Now, the properties 

 characteristic of the parent or parents, at the time of the separa- 

 tion of the germ, must include all of those transmitted to the 

 latter. 



This assists us to understand, why properties of the same 

 kind should all, in a modified form, re-appear in the develop- 

 ment of the offspring (see second paragraph of p. 137) : and, 

 indeed, since it is plain that " every step in development is pos- 

 sible only through the condition preceding,"')- that " becoming 

 depends upon having become, 11 .} we see why those properties can 

 re-appear in a certain order only ; viz. in the order of their ge- 

 nerality in the animal kingdom. 



Thus, in development, the structure characteristic of the 

 Vertebrata only, cannot manifest itself until there has been as- 

 sumed, essentially, a structure common to ammals, of which the 

 Vertebrata are but a part, and to whose type, the type of the 

 Vertebrata is subordinate. In like manner, structures subordi- 

 nate to the type of the Vertebrata, cannot manifest themselves 

 until after a modified appearance of the general type^ of which 

 they are but partial metamorphoses. More and more special 

 forms are thus in succession reached, until the one most special 

 is at length attained. || 



* There is, however, another cause why individuals, even of the same 

 birth, should differ : viz. the different periods, at which the maternal portion 

 of the germs may have been first secreted in the Ovary : for, though conti- 

 nually renewed, they must have, in consequence, a more or less'peculiar state 

 of being. 



f Von Bar, L c. $ Burmeister, L c. 



The necessary appearance, first, of a structure common to animals gene- 

 rally, affords indeed a principal reason for supposing that there is essentially but 

 one fundamental form. 



|| Valentin, an excellent German author, already quoted, says, " the deve- 

 lopment of the animal kingdom, and of the individual animal, are in the ori- 

 ginal idea, throughout, one and the same ; but in the realization of single 

 beings, perfectly different, and elaborated in different directions." The lat- 

 ter he conceives to take place in obedience to " metamorphoses" (a becoming 

 more and more special) " of the original idea." Whether such is the case, 

 we do not now inquire ; but it is due to him, to acknowledge, that if there be 



