THE COLORS OF ANIMALS AND PLANTS. 



535 



differential characters. This principle may, per- 

 haps, however, account for some anomalies of 

 coloration among the higher animals. Thus, Mr. 

 Darwin, while admitting that the hare and the 

 rabbit are colored protectively, remarks that the 

 latter, while running to its burrow, is made con- 

 spicuous to the sportsman, and no doubt to all 

 beasts of prey, by its upturned white tail. But 

 this very conspicuousness while running away 

 may be useful as a signal and guide to the young, 

 who are thus enabled to escape danger by follow- 

 ing the older rabbits, directly and without hesi- 

 tation, to the safety of the burrow ; and this may 

 be the more important from the semi-nocturnal 

 habits of the animal. If this explanation is cor- 

 rect, and it certainly seems probable, it may serve 

 as a warning of how impossible it is, without 

 exact knowledge of the habits of an animal and 

 a full consideration of all the circumstances, to 

 decide that any particular coloration cannot be 

 protective or in any way useful. Mr. Darwin him- 

 self is not free from such assumptions. Thus, he 

 says: "The zebra is conspicuously striped, and 

 stripes cannot afford any protection on the open 

 plains of South Africa." But the zebra is a very 

 swift animal, and, when in herds, by no means void 

 of means of defense. The stripes, therefore, may 

 be of use bv enabling stragglers to distinguish 

 tbeir fellows at a distance, and they may be even 

 protective when the animal is at rest among her- 

 bage — the otdy time when it would need protec- 

 tive coloring. Until the habits of the zebra have 

 been observed with special reference to this point, 

 it is surely somewhat hasty to declare that the 

 stripes " cannot afford any protection." 



The wonderful display and endless variety of 

 color in which butterflies and birds so far exceed 

 all other animals seem primarily due to the ex- 

 cessive development and endless variations of the 

 integumentary structures. No insects have such 

 widely-expanded wings in proportion to their 

 bodies as butterflies and moths ; in none do the 

 wings vary so much in size and form, and in 

 none are they clothed with such a beautiful and 

 highly-organized coating of scales. According 

 to the general principles of the production of 

 color already explained, these long-continued ex- 

 pansions of membranes and developments of 

 surface-structures must have led to numerous col- 

 or-changes, which have been sometimes checked, 

 sometimes fixed and utilized, sometimes intensi- 

 fied, by natural selection, according to the needs 

 of the animal. In birds, too, we have the won- 

 derful clothing of plumage — the most highly-or- 

 ganized, the most varied, and the most expanded 



of all dermal appendages. The endless process- 

 es of growth and change during the develop- 

 ment of feathers, and the enormous extent of 

 this delicately-organized surface, must have beeu 

 highly favorable to the production of varied col- 

 or-effects, which, when not injurious, have been 

 merely fixed for purposes of specific identifica- 

 tion, but have often been modified or suppressed 

 whenever different tints were needed for purposes 

 of protection. 



To voluntary sexual selection, that is, the 

 actual choice by the females of the more brill- 

 iantly-colored males, I believe very little if any 

 effect is directly due. It is undoubtedly proved 

 that in birds the females do sometimes exert a 

 choice ; but the evidence of this fact collected by 

 Mr. Darwin (" Descent of Man," chapter xiv.) does 

 not prove that color determines that choice, while 

 much of the strongest evidence is directly op- 

 posed to this view. All the facts appear to be 

 consistent with the choice depending on a variety 

 of male characteristics, with some of which color 

 is often correlated. Thus it is the opinion of 

 some of the best observers that vigor and liveli- 

 ness are most attractive, and these are, no doubt, 

 usually associated with intensity of color. Again, 

 the display of the various ornamental appendages 

 of the male during courtship may be attractive ; 

 but these appendages, with their bright colors or 

 shaded patterns, are due probably to general laws 

 of growth and to that superabundant vitality 

 which we have seen to be a cause of color. But 

 there are many considerations which seem to 

 show that the possession of these ornamental 

 appendages and bright colors in the male is not 

 an important character functionally, and that it 

 has not been produced by the action of voluntary 

 sexual selection. Amid the copious mass of 

 facts and opinions collected by Mr. Darwin as to 

 the display of color and ornaments by the male 

 birds, there is a total absence of any evidence 

 that the females admire or even notice this dis- 

 play. The hen, the turkey, and the pea-fowl, go 

 on feeding while the male is displaying his finery, 

 and there is reason to believe that it is his per- 

 sistency and energy rather than his beauty which 

 wins the day. Again, evidence collected by Mr. 

 Darwin himself proves that each bird finds a mate 

 under any circumstances. He gives a number 

 of cases of one of a pair of birds being shot, and 

 the survivor being always found paired again al- 

 most immediately. This is sufficiently explained 

 on the assumption that the destruction of birds 

 by various causes is continually leaving widows 

 and widowers in nearly equal proportions, and 



