508 Bibliographical Notices. 



the growth of the hair by tugging of tho teeth or hands in the 

 combats of mature males. But, as Mr. Cuiiiiiugham remarks, " It 

 is unlikely that men should tight in the way suggested after they 

 had reached even the stage of evolution known to us in the lowest 

 existing savages, for they seem always to tight with weapons." 

 Thus, from the dawn of man's evolution the stimulation which 

 Mr. Cunningham invokes has ceased to act, at least with any degree 

 of periodicity ; therefore by the tenets of his faith these secondary- 

 sexual characters should have disappeared, from disuse. After all, 

 as Mr. Cunningham remarks, " what is wanted is evidence con- 

 cerning the influence of mechanical irritation of the hair-follicles in 

 the growth of the hair." 



The common fowl, we are reminded, in fighting erects the long 

 neck-hackles, " which accounts for their elongation," The blows of 

 the beak upon the head received during these contests had similarly 

 been made to account for the comb and wattle. The crest of the 

 peacock has been produced, we are solemnly informed, like the 

 comb of the common cock, by strokes of the beak, which, being less 

 violent, have plucked at the feathers instead of injuring the skin, 

 and so causing an outgrowth from it. 



Are we to account in the same way for the two remarkable 

 feathers which depend, one on either side of the head, in the King 

 of Saxony's Bird of Paradise ? or the wonderful balls of down which 

 invest the legs of the humming-birds of the genus Spathura ? 



The brilliantly coloured bare skin of the cassowary is the result 

 of the irritation, we are asked to believe, " produced by the blows of 

 the beaks of the birds when fighting .... the habit of fighting with 

 the beak also explains the presence of the bony crest on the skull." 



As a matter of fact the cassowary fights not with the beak, but 

 with the legs, which by powerful down- strokes can inflict serious 

 injuries. No one who knows anything of the structure of the 

 helmet of the cassowary would suggest that its existence was due to 

 blows of the beak. 



We venture to think that the above instances are indicative that 

 Mr. Cunningham has failed to seriously injure the case for sexual 

 selection, which, as yet, it must be admitted, holds the field, even 

 though it may fail to satisfy us as an explanation of all the problems 

 which it is called upon to solve. 



As a whole we may say of this book that it contains many new 

 things and many good things ; but the new things are not good and 

 the good things are not new. Nevertheless it will doubtless be 

 widely read and will find a place on the bookshelves even of those 

 who differ from Mr. Cunningham on this very imxjortant subject. 

 It is well printed, well illustrated, and nicely got up. 



In the little work on ' Colour in Nature ' we have an undoubtedly 

 important contribution which will enable us to test the value of 

 much that has hitherto been of a purely speculative nature. The 

 book has probably by this time become tolerably well known. To 

 those who have not yet made its acquaintance we would recommend 

 it as an extremely interesting and helpful work. 



