HEREDITY. 467 



some of them are due to mechanical causes acting 

 after birth. 



The demonstration of the mechanical origin of a 

 given peculiarity, however, by no means precludes 

 that such peculiarity may not be an inheritance from 

 or reversion to pithecoid ancestors. It has been al- 

 ready pointed out that all of the form characters of 

 the vertebrate skeleton, and for that matter, of the 

 hard parts of all animals, have been produced by mus- 

 cular pressures and contractions, and the friction, 

 strains, and impacts, due to these. The demonstra- 

 tions by Virchow and others that such is the origin of 

 the platycnemic human tibia, is directly in the line of 

 Neo-Lamarckian evolutionary doctrine, and shows us 

 that atavistic and reversionary characters are found in 

 the muscular system as well as in the skeleton. Such 

 characters are inheritable as well as those of the skel- 

 eton. But the characters of the skeleton can generally 

 be shown to be inherited, because they appear before 

 birth, and are found at some stage or another of foetal 

 life. The later appearance of the muscular structures 

 in the ontogeny, is simply a case of caenogeny, where 

 the record has been falsified by retardation of the parts 

 in question. 



The variations in the characters of the human skel- 

 eton are of very various significance and value, and 

 the zoologist and paleontologist can perceive that they 

 are sometimes misinterpreted by archeologists. Thus 

 the presence of wormian (Inca) bones, and of a per- 

 foration of the olecranar fossa, have no zoological 

 value ; while the prognathous jaws, tritubercular mo- 

 lar, and platycnemic tibia have such a value. The 

 tufted hai,r of the negro has a human value only, as it 

 does not occur in any of the Quadrumana. But arche- 



