WAEyCCG COLOEATIOy. 173 



have been largely neglected by those "who have thought and 

 written npon the subject ; but it may be reasonably urged that 

 one would not expect to meet with valuable physiological 

 observations in a work devoted to a small group of Annelids. 



Dr. Eisig points out, as has been already mentioned in this 

 book (p. 127), that pigment in the skin has been actually 

 proved in some cases to be excreted matter ; and it may be so 

 in other cases where no direct e\'idence is forthcoming. 



In earlier times, when there were no birds — and after all, 

 the chief enemies of caterpillars are birds — brilliant colora- 

 tion, due to abundant and varied pigment, would be the rule. 

 Dr. Eisig is of opinion that this pigment is itself largely the 

 cause of the distastefulness.* If so, we arrive at an interesting 

 conclusion — that the br ill iant colours (i.e. the ahundunt s^cretion 

 of ijigrrusnt) ha>:e caused the inedihilit'/ of the species, rafh'r 

 fha?>. that the inedihilif'/ has necessitated tlte prod action of bright 

 colour as an advert i seme id. 



This is an important alteration in the usual view of warning 



colours ; but it is obviously not entirely antithetical to the 



■\dews of "Wallace, Poulton, and others ; for we may still snp- 



pose that the bright colours are actually ''warning" coLjurs, 



although they have not been evolved for this express purpose. 



On the view advocated here brUliant coloration is the 



normal condition of caterpillars : the advent of bird-Hfe 



proved a disastrous event for these animals, and compelled 



them to undergo various modifications, except in the ca>e of 



those forms which combine brilliant coloration with nnea^alile- 



ness. 



Dr. Eisig's ingenious suggestion may possibly apply to 



* I may remark that a Cthus monkey sucked a Magpie caterpillar, and 

 tbrew away the skin, as a boy sucks an orange and disposes of the peel. 

 This is so far evidence that the pigmented skin is the distasteful part. 



