EXTENSIONS OF DARWINISM 283 



have most offspring who were equally or even more hijrhly 

 gifted; and thus there would arise a continually increasing 

 vitality whicli would be partly expended in the further develop- 

 ment of those ornaments and plumes which are its result and 

 outward manifestation. The varvine^ conditions of existence 

 would determine the particular part of tlie body at which such 

 accessory ornaments miglit arise, usually^ no doubt, directed 

 by utility to the species. Thus the glorious train of the pea- 

 cock might have begim in mere density of plumage covering 

 a vital part and one specially subject to attack by birrls or 

 beasts of prey, and, once started, these plumes would continue 

 to increase in number and size, as being an outlet for vital 

 energy, till at last they became so enormously lengthened as 

 to become dangerous by their weight being a check to speed 

 in running or agility in taking flight. This is already the 

 case with the peacock, which has some difficulty in rising from 

 the ground and flies very heavily. Its enemies in India are 

 tigers and all the larger members of the cat-tribe, and when 

 any of these approach its feeding-grounds it takes alarm and 

 at once flies up to the low^er branches of large trees. In the 

 ArgTis-pheasant it is the secondary wing-featliers that are ex- 

 ceedingly long and broad, so as to be almost as much a liin- 

 drance to strong or rapid flight as is the train of the pea- 

 cock; and in both birds these ornamental plumes have evi- 

 dently reached the utmost dimensions compatible with the 

 safety of the species. 



There can also be little doubt that in manv of the birds- 

 of-paradise and of the humming-birds, in the enormous crest 

 of the umbrella-bird, in the huge beaks of the hornbiils and 

 the toucans, in the lenc^thv neck and lec:s of the flaminc:os and 

 the herons, these various oraamental or usefid appen(iag(\>< liave 

 reached or even overpassed the maximum of utility. In an- 

 other class of animals we have the same phenomenon. The 

 expansion of the wings in butlerflies and motlis reaches a 

 maximum in several distinct families — the Papilionidre, the 

 Morphidffi, the Bond\vces, au'l the Xoctuje, in all <>f whirli it 



