H 4 FOOT-NOTES TO EVOLUTION. 



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 evi- 

 dent 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 may be mentioned the following : The 

 derivation of the long hind legs of jumping animals, the 

 long fore legs of climbing animals, 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. 



(y) Another whole class of arguments may be re- 

 duced to this proposition : Because necessary mechan- 

 ical conditions are never violated by 

 Mechanical organisms, therefore modifications due 



conditions. . .... 



to such conditions show the inheritance 



of acquired characters. Plainly, the alternative propo- 

 sition is this: If acquired characters are not inherited, 

 organisms ought to do impossible things. 



(z) Many of the arguments advanced to prove the 

 inheritance of characters acquired through use or dis- 

 use seem to me to prove entirely too much. For ex- 



* R. T. Jackson. Memoirs Boston Soc. Nat. Hist., 1890. 



