72 INFLUENCE OF HORMONES 



the periosteum of a bone is destroyed or removed 

 the bone dies, and is then either absorbed, or 

 separated from the living bone adjoining, by ab- 

 sorption of the connecting part. In the stag both 

 skin and periosteum are removed from the antler : 

 probably they would die and shrivel of their own 

 accord by hereditary development, but as a matter of 

 fact the stag voluntarily removes them by rubbing 

 the antler against tree trunks, etc. When the bone is 

 dead the living cells at its base dissolve and absorb it, 

 and when the base is dissolved the antler must fall off. 

 The adaptive relation is not the only common 

 characteristic of these somatic sexual characters. 

 Another most important fact is not only that they 

 are fully developed in one sex, absent or rudi- 

 mentary in the other, but that their development 

 is connected with the functional maturity and ac- 

 tivity of the gonads. There is usually an early 

 immature period of life in which the male and 

 female are similar, and then at the time of puberty 

 the somatic sexual characters of either sex, gener- 

 ally most marked in the male, develop. In some 

 cases, where the activity of the gonads is limited to a 

 particular season of the year, the sexual characters 

 or organs are developed at this season, and then 

 disappear again, so that there is a periodic develop- 

 ment corresponding to the periodic activity of the 

 testes or ovaries. Stags have a limited breeding or 

 ' rutting ' season in autumn (in north temperate 

 regions), and the antlers also are shed and developed 

 annually. In this case we cannot assert that the 

 development of the antler takes place during the 

 active state of the testes. The antlers are fully 

 developed and the velvet is shed at the commence- 



