Chap. IV. MANNER OF DEVELOPMENT. 117 



their lesser height. This shortness of the arms is 

 apparently due to their greater use, and is an un- 

 expected result; but sailors chieily use their arms in 

 pulling and not in supporting weights. The girth of 

 the neck and the depth of the instep are greater, whilst 

 the circumference of the chest, waist, and hips is less in 

 sailors than in soldiers. 



Whether the several foresfoins: modifications would 

 become hereditary, if the same habits of life were fol- 

 lowed during many generations, is not known, but is 

 probable. Rengger 22 attributes the thin legs and thick 

 arms of the Payaguas Indians to successive generations 

 having passed nearly their whole lives in canoes, with 

 their lower extremities motionless. Other writers have 

 come to a similar conclusion in other analogous cases. 

 According to Cranz, 23 who lived for a long time with the 

 Esquimaux, " the natives believe that ingenuity and 

 " dexterity in seal-catching (their highest art and virtue) 

 " is hereditary ; there is really something in it, for the 

 " son of a celebrated seal-catcher will distinguish him- 

 " self though he lost his father in childhood." But in 

 this case it is mental aptitude, quite as much as bodily 

 structure, which appears to be inherited. It is asserted 

 that the hands of English labourers are at birth larger 

 than those of the gentry. 24 From the correlation which 

 exists, at least in some cases, 25 between the development 

 of the extremities and of the jaws, it is possible that 

 in those classes which do not labour much with their 

 hands and feet, the jaws would be reduced in size from 

 this cause. That they are generally -smaller in refined 

 and civilised men than in hard-working men or savages, 



22 * S'augetkiere yon Paraguay,' 1830, s. 4. 



23 ' History of Greenland,' Eng. translat. 1767, vol. i. p. 230. 



24 ' Intermarriage.' By Alex. Walker, 1838, p. 377. 



25 ' The Variation of Animals under Domestication,' vol. i. p. 173. 



