166 ACQUIRED CHARACTERS sec. 



of a sternal keel for the attachment of the pectoral muscles 

 in flying and burrowing animals, in birds, bats, moles, etc. 



It is frequently possible in such cases to form definite 

 conclusions as to the future form of organs which at pres- 

 ent are seen in process of modification. Thus my friend 

 Wiedersheim in a very interesting paper ^ has recently drawn 

 attention to some facts in human anatomy which indicate 

 the future modification of the human body, assuming that 

 existing causes continue to act. In man certain muscles are 

 now increasing, namely, the adductors of the thumb and the 

 musculi glutaei, in the face the mimetic musculature is on 

 the increase, the pelvic girdle is increasing, the ilia are becom- 

 ing wider apart — and all this in addition to the degeneration 

 of organs through disuse, which in a still higher degree 

 indicates the future structure of man. 



It is clear that the progressive development of the in- 

 telligence has likewise gradually effected the increase in the 

 size of the cranium in proportion to the facial part of the 

 skull in man, by means of the increased size of the brain, so 

 that the brain case now forms the principal part of the skull. 

 But it appears that in the most highly developed races of 

 man, provision is made for the farther increase of the brain- 

 case : as Gratiolet has pointed out, in these races the union 

 of the cranial sutures proceeds from behind forwards, so 

 that a greater development of the frontal lobes, on which 

 intelligence depends, is rendered possible ; or rather, the 

 vigorous growth of the frontal lobes has conversely given rise 

 to this arrangement. In the lower races of man the union of 

 the sutures proceeds from before backwards, as in the apes.^ 



I forbear here to enter more minutely into the importance 

 of the inheritance at particular ages of life of characters 



^ R. Wiedersheim, Der Bau des Menschen'als Zeugniss fur seine Vergangenheit, 

 Freiburg i.B. 1887. ^ Cf. Wiedensheim, op. cit. 



