[16 THE DESCENT OF MAN. [Part I. 



even without measurement, that these peculiarities had all 

 decreased ; and on measurement their bodies were found 

 not to be so much elongated as those of the men on the 

 high plateau ; while their femora had become somewhat 

 lengthened, as had their tibiae, but in a less degree. The 

 actual measurements may be seen by consulting Mr. 

 Forbes's memoir. From these valuable observations, there 

 can, I think, be no doubt that residence during many gen- 

 erations at a great elevation tends, both directly and indi- 

 rectly, to induce inherited modifications in the proportions 

 of the body. 83 



Although' man may not have been much modified dur- 

 ing the latter stages of his existence through the increased 

 or decreased use of parts, the facts now given show that 

 his liability in this respecfr has not been lost ; and we posi- 

 tively know that the same law holds good with the lower 

 animals. Consequently we may infer that, when at a re- 

 mote epoch the progenitors of man were in a transitional 

 state, and were changing from quadrupeds into bipeds, 

 natural selection would probably have been greatly aided 

 by the inherited effects of the increased or diminished use 

 of the different parts of the body. 



Arrests of Development. — Arrested development dif- 

 fers from arrested growth, as parts in the former state 

 continue to grow while still retaining their early condi- 

 tion. Various monstrosities come under this head, and 

 some are known to be occasionally inherited, as a cleft- 

 palate. It will suffice for our purpose to refer to the 

 arrested brain-development of microcephalous idiots, as 

 described in Vogt's. great memoir. 84 Their skulls are 



33 Dr. Wilckens (' Landwirthschaft. Wochenblatt,' No. 10, 1869) has 

 lately published an interesting essay showing how domestic animals, 

 which live in mountainous regions, have their frames modified. 



8 * 'Memoire sur les Microcephales,' 1867, pp. 50, 125, 169, 171, 184, 

 198. 



