ON CATAGEJ^ESIS. 423 



individuals which spring from it, provided the acquired changes 

 be common to both sexes or to those which produce new indi- 

 yiduals. " 



The same projoosition was previously enunciated by Lamarck 

 in the following condensed form ("^Recherches sur les Corps 

 Vivans," p. 50) : 



" It is not the organ, that is, the nature and form of the parts 

 of the body, which have given origin to its habits and peculiar 

 functions, but it is, on the contrary, its habits, its manner of life, 

 and the circumstances in which individuals from which it came 

 found themselves, which have, after a time, constituted the form 

 of the body, the number and character of its organs, and the func- 

 tions which it possesses." 



Several years ago, not having read Lamarck, I characterized 

 the above hypothesis as the " law ot use and effort," * and I have 

 subsequently formulated the modus operandi of this law into two 

 propositions. The first of these is, that animal structures have 

 been produced, directly or indirectly, by animal movements, or 

 the doctrine of hinetoge^iesis ; the second is, that as animal move- 

 ments are primitively determined by sensibility, or consciousness, 

 consciousness has been and is one of the primary factors in the 

 evolution of animal forms. This is the doctrine of arcluBsflipi- 

 ism. The doctrine of kinetogenesis is implied in the speculations 

 of Lamarck in the following language ('' Philosophic Zoologique," 

 ed. 1830, p. 239): ''With regard to the circumstances which 

 [Nature] uses every day to vary that Avhich she produces, one can 

 say that they are inexhaustible. The principal arise from the 

 influence of climates ; from diverse temperature of the atmos- 

 phere and of the environment generally ; from diversity of loca- 

 tion ; from habits, the most ordinary movements, and most fre- 

 quent actions," etc. The influence of motion on development is 

 involved in Spencer's theory of the origin of vertebrae by strains ; \ 

 and I have maintained the view that the various agencies in pro- 

 ducing change mentioned by Lamarck are, in the case of animals, 

 simply stimuli to motion. | The immediate mechanical effect of 

 motion on animal structure has been discussed in papers by Ryder, 



* " Method of Creation," " Proceedings American Philosophical Society,'' 1871, p. 



247. 



t "Princi[)les of Biology," II, p. 195. 



X " On the Relation of Animal Motion to Animal Evolution," "American Natural- 

 ist," Jan., 1878. 



