K. E. VON BAER. PHILOSOPHICAL FRAGMENTS. 187 



with so much applause as this : that the higher forms of animals 

 in the single stages of the development of the individual, from its 

 first origin to its completed development, answer to the permanent 

 forms of the animal series, and that the development of each ani- 

 mal follows the same laivs as that of the whole animal series ; 

 thai therefore the more highly organized animal in its individual 

 development passes essentially through the permanent forms which 

 lie beloiv it, so that the periodical differences of the individual 

 may be referred to the differences of the permanent animal forms. 



This idea, springing into existence at a time when no con- 

 nected investigation (except those of Malpighi and Wolff) into 

 the earlier periods of development of any animal had been in- 

 stituted, and principally carried out by a man who perhaps pos- 

 sessed more knowledge than any one else of the course of de- 

 velopment of the higher organisms, could not fail to be widely 

 accepted, since it was supported by a multitude of special de- 

 monstrations. It acquired yet greater influence, by its fruitful 

 application to the explanation of a series of monstrosities, which 

 were regarded as the consequences of a partial arrest of deve- 

 lopment in its earlier periods. It is no wonder then that it was 

 warmly received and rigorously carried out. 



Certain of its advocates were so zealous, that they no longer 

 spoke of similarity, but of perfect identity, and assumed that the 

 correspondence had been demonstrated in all cases and to the 

 minutest details. A short time since we read in a paper upon 

 the circulation in the embryo, that there was no animal form 

 through which the embryo of man omitted to pass. By degrees 

 it became the custom to look upon the different forms of animals 

 as developed out of one another, and then many appeared to 

 forget that this metamorphosis was after all only a mode of con- 

 ceiving the facts. On the strength of the observation that no 

 vertebral remains are to be found in the older strata, it was con- 

 cluded that there was historical evidence for such a metamor- 

 phosis of the different forms of animals, and at length, in sober 

 seriousness, and with all due particularity, we were informed 

 exactly how they arose from one another. Nothing could be 

 easier. A fish, swimming towards the shore, desires to take a 

 walk, but finds his fins useless. They diminish in breadth for 

 want of use, and at the same time elongate. This goes on with 



