DURATION OF SPECIES. 349 



of some species or form in particular, not of specie3 

 or forms generally, which, for the most part, may and 

 do vary sufficiently, and in varying survive, seeming- 

 ly none the worse, but rather the better, for their 

 long tenure of life. 



The opposite idea, however, is maintained by M. 

 Isaudin, 1 in a detailed exposition of his own views of 

 evolution, which differ widely from those of Darwin 

 in most respects, and notably in excluding that which, 

 in our day, gives to the subject its first claim to scien- 

 tific (as distinguished from purely speculative) atten- 

 tion ; namely, natural selection. Instead of the causes 

 or operations collectively personified under this term, 

 and which are capable of exact or probable apprecia- 

 tion, M. Kaudin invokes " the two principles of 

 rhythm and of the decrease of forces in Mature." 

 He is a thorough evolutionist, starting from essential- 

 ly the same point with Darwin ; for he conceives of 

 all the forms or species of animals and plants "comme 

 tire tout entier d'un protoplasma primordial, uniform, 

 instable, eminemment plastique." Also in " Integra- 

 tion croissante de la force evolutive a mesure qu'elle 

 se partage dans les formes produites, et la decrois- 

 sance proportionelle de la plasticite de ces formes a 

 mesure qu'elles s'eloignent davantage de leur ori- 

 gine, et qu'elles sont mieux arretees." As they get 

 older, they gain in fixity through the operation of the 



1 "Les Especes affines et la Theorie de rEvolution," par Charles 

 Naudin, Menibre de l'Institut, in Bulletin de la Socieie Botaniquc de 

 France, tome xxi., pp. 240-272, 1874. See also Comples Bendus, Sep- 

 tember 27 and October 4, 1875, reproduced in " Annales des Sciences 

 Naturelles," 1876, pp. 73-81. 



