CONTEMPORARY EVOLUTION OF MAN. 39 



V. Muscular variations. The law of muscular evo- 

 lution. Specialization by the separation of new 

 independent contractile bands from the large funda- 

 mental muscles. Muscular degeneration leads to for- 

 mation of non-contractile ligaments. 



Muscular anomalies. (1) Palseogenetic reversions ; 

 complete restoration of lost muscles. (2) Neogenetic 

 reversions ; revivals of former relations in existing 

 muscles. (3) Progressive variations ; pointing to fu- 

 ture type by specialization, or degradation. (4) For- 

 tuitous variations. (A) In upper limb, (a) Flexor 

 longus pollicis and flexor digitorum. (6) Palmaris 

 longus. In infants and lower races. Increase of 

 muscles in lower arm and hand, and the consequent 

 specialization, (c) Retrogression in muscles of shoul- 

 der and upper arm. (B) In lower limb. Muscles of 

 foot, 



VI. Centers of variability ; while variation is uni- 

 versal, it rises to a maximum in those regions of most 

 active evolution. In man these centers are in the 

 forearm and hand for the muscular system. 



VII. Particulate inheritance, and correlated vari- 

 ation. 



