THE THEORIA GENERATIONIS. 269 



tion. Aristotle even believed that mud could become earth- 

 worms and earthworms become eels.^ 



Before the end of the past century these two views of devel- 

 opment which I have attempted to trace back respectively to 

 Aristotle and Plato had assumed definite and contrastins: 

 forms. Bonnet, Haller, and Leibnitz, following a Platonizing 

 tendency in dealing with natural phenomena, had elaborated 

 and accepted the theory of cmboite7nent , or " evolution," as 

 the word was then understood. Bonnet's contributions to this 

 view have been adequately presented by Professor Whitman, in 

 his lectures to the members of the Marine Biological Laboratory 

 during the summer of 1894.2 Haller, justly styled by his con- 

 temporaries an " abyss of learning," though devoted to cmboite- 

 ment, had too great a store of mental riches to give himself up 

 year after year, like Bonnet, to exhaustive rumination on a 

 single theory. The opinion of Leibnitz on emboitement is 

 not so generally known, and may be considered briefly. The 

 philosopher of a preestablished harmony could hardly overlook 

 a theory like that of predelineation. Like many philosophers 

 of the present day, Leibnitz was glad to accept the theories of 

 contemporary scientists, weave them into his general scheme, 

 and, without adding anything really new, again present them to 

 the public, heavier with the weight of his name and authority. 

 In his " Monadologie," he says ^ : "Philosophers have had 

 much difficulty in dealing with the origin of forms, entelechies, 

 and souls. Of late, however, careful investigations on plants, 

 insects and animals, have led to the conclusion that in nature 

 organic bodies never arise from chaos or decomposing matter, 

 but always from germs (semen ces), in which, zvithout a doubt, 

 they are already preformed. Hence we may conclude that in 

 this Anlage not only do organic bodies exist before generation, 

 but that there is a soul in these bodies, in a word, the indi- 



1 Aristoteles. '\(jTopLa.i vepi ^uwv. Ed. Aubert u. Wimmer. Leipzig, 1868. 

 ii, 6. 16. pp. 56 and 58. — J. Bona Meyer. Aristoteles Thierkunde. Berlin, 1855. 

 pp. 97, 98. 



2 Whitman, CO. (i) " Bonnet's Theory of Evolution a System of Negations." 

 (2) "The Palingenesis and the Germ Doctrine of Bonnet," Biological Lectures 

 (1894). Boston, Ginn & Co., 1895. 



3 Leibnitz, Op. Phil., p. 711. 



