38 JOURNAL, BOMBAY NATURAL HISTORY SOCIETY, Vol. XVI. 



and hollow-horned ruminants are instances where the character has been partial- 

 ly transmitted to the other sex also. 



Pressed to extremes, however, the theory becomes ridiculous, as when it is 

 sought to explain the hairy chins of men by the supposition that, in primal 

 savagery, men were in the habit of biting each other's chins when fighting. 



It is no criticism of either this or Darwin's theory to ask why it does not 

 exist in all animals, because both theories presuppose an excess of males over 

 females or polygamous habits which amount to the same thing ; as a matter of 

 fact among almost all vertebrates where sexual dimorphism occurs, this is 

 known to be the case. 



Mr. Dewar cites the case of kingfishers and mynas, and asks why, according to 

 Darwin, mynas should not be the more brilliant of the two. But he presupposes 

 that brilliant colours are more difficult to acquire than sombre ones, which 

 in the present state of our knowedge — or ignorance — is not justifiable. 

 The colours of the myna's English cousin — the starling — would, one might 

 suppose, be extremely difficult to acquire, although the general result is quite 

 sombre. 



There are many isolated cases of dimorphism for which special explanations 

 can be offered as in the case of the New Zealand bird, the two sexes of which 

 invariably feed together — one having a beak suited for boring holes in rotten 

 trees, and the other for scooping out the grubs. 



But I would maintain that the majority of cases among vertebrates at least 

 must be explained by the relative incidence in particular cases of a number of 

 laws or tendencies of which I think the following are the four chiefest : — 



(1) The natural tendency of like to produce like. 



(2) The natural tendency of the sexes to be unlike. 



Not sufficient emphasis is laid on this point. The whole course of Natural 

 History — by which I mean the history of the growth of creation from the mos-t 

 primitive forms to the highest — is almost as much a history of the specialisation 

 of the functions of the sexes as of specific structures. 



Without going into detail one need only refer to those organisms of which 

 there is only one sex, to the next series where the two sexes are partially 

 developed, but where parthenogenesis is still the rule and on to the higher forms 

 in which the sexes gradually become more permanent and parthenogenesis rarer. 



(3) The natural tendency of every creature to protect itself from its 

 enemies, either by acquiring weapons of offence or defence or by superficial 

 protective colours or structure. 



(4) The natural tendency of the males of all species whererivalry exists 

 among that sex to disregard (3) in a greater or less degree during the breeding 

 season, when characteristic modifications, the result of pugnacity or sexual 

 admiration or other cause have a chance to come into play. 



I think the action of these four tendencies on the blood, etc., of the males, 

 excited by the procreative instincts, will account in a genera] manner for the 

 facts. 



