128 Kev. J. T. Gulick on the 



any action of the same principle. I liave never maintained 

 that any species can long escape the action of natural selec- 

 tion ; but I have that natural selection cannot produce trans- 

 formation of a race unless it secures the propagation of other 

 than average forms of that race ; that it cannot be a cause of 

 divergence unless to this condition is added the independent 

 generation (/. e. isolation) of groups that are subjected to some 

 diversity in its action ; and that, in isolated groups, some of 

 the divergent characters may be due to other causes of trans- 

 formation. In the passage I have quoted from p. 142 he 

 expresses great confidence in the proof that all specific charac- 

 ters are developed and fixed by natural selection ; but in the 

 discussion that follows concerning the influence of natural 

 selection he claims as belonging to this principle sets of influ- 

 ences which are usually included under sexual selection and 

 which he cannot regard as due to the reactions between the 

 species and its environment (see ' Darwinism,' pp. 282-285), 

 and even then it is found too narrow to cover all the facts of 

 specific divergence ; for when he comes to consider the origin 

 and development of accessory plumes he has to abandon the 

 theory to which he has clung through the greater part of the 

 book. Speaking of the enormously lengthened plumes of the 

 " bird of paradise and of the peacock," he says, on page 293, 

 " The fact that they have been developed to so great an extent 

 in a few species is an indication of such perfect adaptation to 

 the conditions of existence, such complete success in the battle 

 of life, tliat there is, in the adult male at all events, a surplus 

 of strength^ vitality^ and groioih-power^xoMcli is able to expand 

 itself in this toay without injury. That such is the case is 

 shown by the great abundance of most of the species which 

 possess these xconderfil superfluities of plumage. . . . Why^ 

 in allied species, the develojmient of accessory j^lurnes has taken 

 different forms, we are in^ahle to say, except that it may be due 

 to that individual variahility which has served as the starting- 

 point for so much of wliat seems to us to be strange in form 

 or fantastic in colour, both in the animal and vegetable world." 

 (The italics are mine.) According to the theory he has else- 

 where maintained, these superfluities of form and colour which 

 are not controlled by natural selection should present " a series 

 of inconstant varieties mingled together, not a distinct segre- 

 gation of forms" (p. 148) ; but in this passage he teaches 

 that they have assumed different forms in allied species. On 

 p. 141 he maintains that characters which are neither bene- 

 ficial nor injurious are from their very nature unstable and 

 cannot become specific, while here he offers a suggestion as 

 to how they have become specific. There is, then, a problem 



