//. F. O shorn 337 



Morgan believed that this explanation could be applied to all 

 cases of adaptive modification, but it is evident that this cannot 

 be so, because the teeth also undergo the same progressively 

 adaptive evolution along determinate lines as the skeleton, and 

 yet it is well known that they do not improve by use, but rather 

 deteriorate. Thus the explanation is not one which satisfies 

 all cases ; l but it does seem to meet, and to a certain extent 

 undermine, the special cases of evidence of the inheritance 

 of acquired characters, collected by Professor Cope in his well- 

 known papers upon this subject." 



['Organic Selection.' 2 From Science, N. S., Vol. VI., pp. 583-587, Oct. 



15, 1897.] 



" The evidence for definite or determinate variation has 

 always been my chief difficulty with the natural selection 

 theory, and my chief reason for giving a measure of support 

 to the Lamarckian theory. This evidence has steadily accu- 

 mulated in botanical and zoological as well as paleontological 

 researches, until it has come to a degree of demonstration 

 where it must be reckoned with. 3 



" Quite in another field, that of experimental embryology 

 and zoology, the facts of adaptation to new and untoward 

 circumstances of environment have begun to constitute a distinct 

 and novel series of problems. In many cases they are so 



1 These cases do militate against Lamarckian inheritance, but do not, I 

 think, furnish exceptions to the operation of organic selection; for the deterio- 

 ration of the teeth by use would only make more necessary the cooperation 

 of muscular and other accommodations, while variations in the teeth were 

 accumulating (cf. the discussion of ' coincident variation ' above, Chap. 

 XIV. 3, and also that of the universal application of the principle above, 

 Chap. III. i, 5).--J. M. B. 



2 A discussion introduced by Professor Henry F. Osborn and Professor 

 Edward B. Poulton, Detroit Meeting, Amer. Assoc., Aug. n, 1897. 



3 Cf. Chap. XII. I above, where it is pointed out that Professor Osborn 

 is here possibly using the phrase ' determinate variation ' somewhat loosely for 

 ' determinate evolution ' in my opinion a different thing. It is necessary 

 to say this to make entirely valid his kind citations from me. Professor 

 Weldon's exposition of the theory of the 'mean' in Biometrica, I. 3, may be 

 consulted.--!. M. B. 



z 



