EIGHTEENTH CENTURY EVOLUTIONISTS. 247 



heredity we must assume a communication of corporeal elements, 

 vehicles of that heredity, from both sides. And, as Maupertuis also 

 observed, the supposed fact by which Harvey had justified this singular 

 conclusion had already been rendered more than questionable by later 

 investigations of Verheyen. 



Having established these essential principles to his satisfaction, 

 Maupertuis proceeded to formulate an hypothesis concerning the nature 

 of the fundamental physical process presupposed by the facts of her- 

 edity, on the one hand, and of variation, on the other. The formation 

 of an embryo must, he conceived, be due to the combination in a new 

 organic union, of a great number of living corporeal particles, derived 

 usually from both parents, each of which particles carries with it a sort 

 of organic memory (souvenir) of the life of the organism to which it 

 formerly belonged, and thereby tends to unite with the other particles 

 in such a way as to produce a new organism of the same species.* 

 This process of recombination of already living particles was held by 

 Maupertuis to be governed by something more than the laws of 

 mechanism; embryogeny was for him no mere process of juxtaposition, 

 under the laws of gravitation, of so many inert atoms; the ultimate 

 units of the newly constituted living being all possess their own self- 

 contained law of development, and their own distinctive selective 

 affinities for certain other units. None the less, purely mechanical dis- 

 placements of parts also take place; and to these in part, he supposed, 

 is due the occurrence of monstrous forms, and many of the more ordi- 

 nary variations from the hereditary specific type. Moreover, the ele- 

 mentary units which, coming from the parents, combine to form the 

 embryonic offspring, in part carry with them a similar sort of organic 

 memory of the particular and individual characters of the parent, and 

 so tend to develop those characters in that offspring; but in part also 

 they are free from this tendency, and carry with them rather the traits 

 of more remote ancestors (atavism), and some of them may even be 

 wholly independent of hereditary predetermination. It is these espe- 

 cially which, in Maupertuis 's hypothesis,! constitute the explanation of 

 the general tendency to variation in animals, which he recognized to 

 the full. If one must have a further explanation why the transmitted 

 corpuscles tend to reproduce the characters of the parents, Maupertuis 

 suggests that perhaps there enters into the embryo a separate germ 

 from each part of the body of the parent of which the character is repro- 

 duced; in other words, he proposes a hypothesis similar to the Dar- 



*' Venus Physique,' Pt. II., ch. 5. We must suppose 'que la liqueur 

 slminale de chaques espece d'animau, contient une multitude innombrable de 

 parties propres a former par leurs assemblages des animaux de la nieme espece. 



t hoc. cit. It is likewise to be assumed ' que dans la liqueur seminale de 

 chaque individu, les parties propres a former des traits semblables a ceux de 

 cet individu sont celles qui d'ordinaire sont en plus grand nombre, et qui ont 

 le plus d'afnnit€; quoiqu'il y en ait beaucoup d'autres pour des traits difftfrents.' 



