Conklin.] ^^ [May 1, 



(1) In the first place, this whole line of argument starts with the 

 assumption that the indiyitlual habits of an animal are inherited, and 

 that these habits ultimately determine the structure — an assumption 

 which really begs the whole question ; for, after all, the substratum of 

 any habit must be some physical structure, and if modified habits are 

 inherited it must be because some modified structure is inherited. I 

 take an example which will serve as an illustration of a whole class : 

 Jackson* says that the elongated siphon of Mya, the long-necked 

 clam, is due to its habit of burrowing in the mud, or to quote his words : 

 "It seems very evident that the long siphon of this genus was brought 

 about by the effort to reach the surface, induced by the habit of deep 

 burial." It certainly would be pertinent to inquire where it got this 

 habit, and how it happened to be transmitted. It is surely as difficult 

 to explain the acquisition and inheritance of habits, the basis of which 

 we do not know, as it is to explain the acquisition and inheritance of 

 structures which are tangible and visible. Such a method of procedure, 

 in addition to begging the whole question, commits the further sin of 

 reasoning from the relatively unknown to the relatively known ! 



This case is but a fair sample of a whole class, among which maj- be 

 mentioned the following : The derivation of the long hind legs of jump- 

 ing animals, the long fore legs of climbinganimals, and the elongation 

 of all the legs of running animals through the influence of an inherited 

 habit. All such cases are open to the very serious objection mentioned 

 above. 



(2) Another whole class of arguments may be reduced to this propo- 

 sition : Because necessary mechanical conditions are never violated bj- 

 organisms, therefore modifications due to such conditions show the iu- 

 lieritance of acquired characters. Plainly, the alternative proposition 

 is this : If acquired characters are not inherited, organisms ought to do 

 impossible things. 



(3) Many of the arguments advanced to prove the inheritance of 

 characters acquired through use or disuse seem to me to prove entirely 

 too much. For example. Prof. Cope argues very ably that bones are 

 lengthened by both stretch and impact, and that modifications thus pro- 

 duced are inherited. Even granting that this is true, how would it be 

 possible fortius process of lengthening to cease, since in active animals 

 the stretch and impact must be continual? Prof. Cope answers that 

 the growth ceases when "equilibrium" is reached. I confess I cannot 

 understand this explanation, since the assumed stimulus to growth 

 must be continual. But granting again that growth may stop when an 

 animal's legs become long enough to "satisfy its needs," how on this 

 principle are we to account for the shortening of legs, as, for example, 

 in the turnspit dog and the ancon sheep and numberless cases occurring 

 in nature? If any one species was able, by taking thought of mechan- 

 ical stresses and strains, to add one cubit unto its stature, how could 

 the same stresses and strains be invoked to decrease its stature? 



* R. T. Jackson, Memoirs Boston Soc. Nal. Ilist., 1890. 



