226 THE BIOLOGY OF BIRDS 



congeries. The hypothesis is in no wise inconsistent with 

 the view that many sex-characters are transformed species- 

 characters, for the variation in such cases was the trans- 

 forming. Nor does the hypothesis conflict in the least 

 with the facts in regard to the importance of hormones in 

 the individual development of the sex-characters, that is a 

 question in the physiology of development. Nor does the 

 hypothesis conflict at all with the view that some process of 

 Selection favoured the persistence and diff"usion of the new 

 character. The hypothesis concerns the origin, not the 

 ontogenetic development, nor the phylogenetic evolution. 



One of the arguments that may be used in support of 

 our hypothesis is that used in a slightly diff^erent connection 

 in " The Evolution of Sex " (1889). It is this. There are 

 numerous distinctively masculine characters which have 

 some measure of " family resemblance," which look as if 

 they had something in common, which are congruent with 

 the intenser metabolism of the male sex. To a thorough- 

 going Lamarckian this is readily intelligible, for he regards 

 the colour-display, the exuberance of integumentary out- 

 growths, the erection of parts of the body such as crests and 

 tail-feathers, the growth of weapons on the one hand and 

 embracing organs on the other, as natural developments of 

 the intensely living, lusty male, as natural individual develop- 

 ments, whose results have gradually been incorporated in the 

 heredity-bundle. But we cannot take this view of the matter. 

 We do not believe that Nature works in this direct way. 

 Our suggestion is that such measure of congruence as there 

 is in, say, masculine sex-characters {e.g. brighter colouring, 

 exuberant decoration, smaller size) may be hypothetically 

 interpreted as due to their having arisen as germinal varia- 

 tions or mutations in germ-cells predetermined to develop 

 into males. 



As a subsidiary hypothesis, we venture to suggest that 

 augmentations of the activity of the gonadial glands (due 

 either to germinal or to nurtural causes) may have from time 

 to time set free in the organism an unusual abundance of 

 hormones with a corresponding exaggeration of individual 



