]54 



Dr. W. Kowalevsky on the 



[Feb. 6, 



fold mode of reduction of the manus and pes, — a simple or inadaptive, and 

 an elaborate or adaptive, mode. 



Following the first or inadaptive mode of reduction, the foot, whilst 

 losing its lateral digits, acquires no better adaptation to altered con- 

 ditions of locomotion and support of the body than that which is de- 

 rived from the mere thickening of the remaining digits. The rela- 

 tion between the carpal and tarsal bones and the remaining two middle 

 metacarpals and metatarsals remains just the same as it was in the 

 tetradactyle ancestor. The remaining digits do not exhibit any modifi- 

 cation by which they receive more ample support from the carpal 

 aud tarsal bones, by taking the place formerly occupied by the now re- 

 duced and lost lateral digits. This mode of reduction I call inadaptive, 

 or reduction in which inheritance is stronger than modification. As an 

 instance of this inadaptive mode of reduction, I may point out the foot of 

 Anoploiherium and Xiphodon. The annexed diagram clearly illustrates 



