575- '233 



The Species, the Sex, and the Individual 



Part II. 



I HAVE been discussing characters that are related to sexual court- 

 ship, but among characters confined to one sex there are others 

 which are connected with other actions. For instance, there are struc- 

 tural peculiarities which are only employed in combat. Among the 

 most highly developed of these are the antlers of stags. It cannot 

 be disputed that these are the special, apparently the only weapons 

 of the stao\ and that there is no stag in a state of nature which does 

 not regularly follow the practice of duelling without any variation 

 in the arms employed. But those who consider that the evolution 

 of the antlers is sufficiently explained by the constant victory and 

 survival of the stags which have them most developed, leave out of 

 view important problems: — Firstly, why do the antlers only begin 

 to develop when the stag becomes mature ; Secondly, why are they 

 renewed every summer, and drop off again in spring ? In relation 

 to these problems it is at least significant that the males only fight 

 when they begin to breed, and, when mature, only in the breeding 

 season, which is limited to the autumnal months. As the fighting 

 of stags is fierce and frequent, it is quite possible that the irritation 

 due to butting with the forehead was the exciting cause in the 

 beginning, and has been ever since, of the remarkable outgrowth of 

 bony tissue which forms the antlers. If this were so, it would be 

 physiologically intelligible that when the stimulation ceases at the 

 end of the butting season and the circulation becomes less active, 

 the bone should cease to grow, should become dry and brittle, and 

 then tin; antlers should either drop off of their own accord, or 

 be intentionally broken off by the stag. Next season a renewal of 

 the fighting would cause a renewal of the growth. My theory is, 

 that stimulations periodically repeated, physiologically cause periodi- 

 cal phenomena of growth, and that these rhythmical processes of 

 growth repeated in successive generations ultimately become heredi- 

 tary. It is, or has been, a current belief that effects so caused are 

 not inherited ; but such inheritance has not yet been proved to be 

 impossible. I am only attempting to show that the facts seem to 

 lead inductively to the conclusion that structural evolution has 



