Introduction: Variation. QJ 



female is also easily to be understood on the ground of the elimination of the 

 disadvantageously coloured birds of this sex, yet the explanation does not seem 

 to apply to the majority of cases, in many of which the female is like the male, 

 and in others she is only a little less bright or -U-ants some special marking 

 and appears then to represent a lower stage in the history of the race, as the 

 immature male is often like her. Many males assist in incubation. The female 

 of the Cuckoo, Eudynamis, which lays its eggs in Crows' nests does not appear 

 to be protectively coloured, but the male, being black, might be thought to be so. 



Darwin's theory of sexual selection has been much contested of late years. 

 The author cites cases of certain female birds in captivity mating by preference 

 with certain males and avoiding others; though allowance must perhaps be made 

 for this in nature, there is now a strong opinion in favour of the view of a 

 passive role being generally played by the female, the male expelling his rivals 

 and making the. female yield to him. 



There is much to be said for Mr. Wallace's view of an excess of vitality 

 or growth-force in the male as the cause of the development of superfluous 

 decorative plumes, etc., though a localization of such growths in the skin "over 

 centres of high nervous or muscular activity" is not tenable. For instance, the 

 second primary of the male Macrodipteryx, an African Nightjar, is developed 

 into an enormous racket-feather capable of erection ; three long racket-feathers 

 sprout from each side of the head of the male of the Paradise-bird, Parotia, one 

 very long one in Pteridophora, etc., etc. As the principal muscular and nervous 

 centres are not difl"erent in birds, such a great diversity in the location of the 

 accessory growths could not arise from this cause. Why does the male Paradisea 

 have its ornamentation chiefly on the side of the breast, and another Bird of 

 Paradise, Lophorhina, on the occipital region and jugulum? 



Mr. Wallace's theory appears to include "the normal development of colour 

 due to the complex chemical and structural changes ever going on in the 

 organism" (Darwinism, p. 288), for the sex which possesses the most growth- 

 force will be the first to undergo these necessary modifications. It is probable 

 that a great number of sexual difl'erences owe their origin to this developmental 

 law. (See Loiiculus, antea p. 57). 



Mr. Stolzmann portrays the two sexes as naturally inimical to one another's 

 well-being. The males above a certain number are useless parasites, they diminish 

 the food-supply and persecute the females; ill-fed females produce an excess 

 of male offspring, and the female for her own preservation produces males which 

 are disastrously equipped for the struggle for existence. We are unable to 

 grasp the argument, if indeed it is a valid one, for it appears to us that the 

 handicapped males will be the first to perish, and the males Avhich will per- 

 petuate the species will be the sons of females which produce the best-equipped 

 offspring. Their qualities being inherited, these males will somewhat counteract 

 the tendency on the part of certain females to produce inferior males, and the 

 latter females will be less likely to survive than their sisters. As their inferior 



