192 K. E. VO\ BAER. — rHl LOSOPII ICAL FRAGMENTS. 



1. That no conditions can obtain in embryos which are not 

 permanent in at least some animals. There exists, however, no 

 animal which carries about its nutriment with it, as the embryo 

 carries its yelk. No animal has a protruded portion of the in- 

 testine, such as the yelk-sac. But from the development of 

 Birds, and of some Mammalia (especially of the Carnivora), in 

 which this yelk-sac remains for a very long period, up to a time 

 when all the characters of the Bird's or Mammal's body are 

 either fuU}^ present or nearly so, we ought to conclude that many 

 such animals exist. Among Mammals the incisor teeth are 

 developed before any others. No animal, however, has a per- 

 manent dentition consisting of incisor teeth only. 



2. In like manner, however, as the relations of the embryo 

 produce forms in it like the protruded intestinal sac, which 

 occur in no permanent animal, do they render it impossible that 

 many large groups of animals should be repeated. Thus the 

 essential characters of Insects, their active relation to air, cannot 

 be repeated in them ; therefore, also, the Mammalian embryo 

 can never resemble the perfect Bird. 



3. Furthermore, the embryo of the higher animals, in any 

 stage of its development, should not agree with a single character 

 only of some permanent form, but with its totality, even although 

 the peculiar relations of the embryo should exclude certain cor- 

 respondences. If it be argued, for instance, that certain cha- 

 racters must be peculiar to, and permanent in, the embryo as 

 such ; that, for example, it is only because as an embryo it is 

 dependent for nourishment upon the maternal body, that it has 

 a protruded yelk-sac, and in this respect cannot correspond with 

 a permanent form; yet those relations in which there is an 

 agreement here and there* must be common to all. This, how- 

 ever, is not the case. If I ascribe to the embryo, so long as its 

 two cardiac ventricles are not yet separated, and the fingers are 

 not divided from one another, the organization of a Fish, yet I 

 find no compressed tail, nor a thousand other characteristics 

 which very early appear in Fishes. 



It is just the same with whatever permanent animal form I 

 compare the embryo of a higher form. It is said that the Ce- 

 tacea are foetus-like [i. e. resemble the embryos of higher animal 

 * i. e. which are not necessarily connected with embryonic existence ? — Tr, 



