BIOGENETIC LAW 69 



that transformations could arise by means of monstrous 

 development (p. 86). In this connection the experiments 

 which he made on the hen's egg 1 in order to produce 

 artificial monstrosities are significant, though his purpose was 

 rather to obtain proof of the inadequacy of the preformation 

 hypothesis. 2 



It seems probable enough that if Geoffrey had developed 

 his views on evolution he would finally have been led to 

 interpret unity of plan in terms of genetic relationship. But 

 as it was he remained at his morphological standpoint. He 

 did not interpret rudimentary organs as useless heritages of 

 the past ; he preferred to think that Nature had prepared 

 double means for the same function, one or other being 

 predominant according as the animal lived in the water or on 

 the land. "To the animal that lives exclusively in the air 

 Nature has granted an organisation suited to this mode of 

 respiration, without however suppressing the other corre- 

 sponding means, that is to say, without depriving it of a 

 second system which is applicable only to the mode of 

 respiration by the intermediary of water, and vice versa." 3 



He seems, in one instance at least, to have hit upon the 

 root-idea of the biogenetic law, but he was far from 

 appreciating its significance. He recognised that an 

 amphibian in its development passed through a stage when 

 it was in all essentials similar to a fish, and he saw in this 

 visible transformation a picture of the evolutionary transfor- 

 mation. " An amphibian," he writes, 4 " is at first a fish under 

 the name of tadpole, and then a reptile [sic] under that of 

 frog. ... In this observed fact is realised what we have 

 above represented as an hypothesis, the transformation of 

 one organic stage into the stage immediately superior." But 

 it is not clear that he considered the development of the 

 amphibian to be a repetition of its ancestral history. 



He went, however, a certain length towards recognising 

 the main principle of a law which was a commonplace of 



1 Mem, Mus. d'Hisf. nat., xiii., p. 289, 1826. 



2 Mem. Mus. (PHist. naf., xviii., p. 221, 1828. His teratological 

 work is important, and is chiefly contained in the second volume of the 

 Philosophic anatomique. 



3 Phil, anaf., i., p. 449. 



. Acad. Sci. t xii., p. 82, 1833. 



