330 THE ZOOLOGIST. 



an ancient geological record, it is also in that phase of animal existence 

 that the beginnings of colouration must have developed. It therefore 

 seems possible that assimilative colouration may have been a first and a 

 very general consequent in animal development ; and that the subsequent 

 protective resemblance acquired by numerous living creatures through the 

 process of natural selection, when life had advanced to the competitive 

 stage, is far too frequently used as an explanation for whole series of 

 uniform phenomena in colouration, which have probably survived unaltered 

 from remote antiquity." (Pp. 383, 384.) And again: "As adaptation im- 

 plies a previous state of variation, which again predicates a more or less stable 

 condition from which variation arose, we come to the conclusion that the 

 pre-variable condition was a unicolorous one, and from the data — scanty 

 indeed — at our disposal, are inclined to suggest that the unicolorous hue 

 was originally due to assimilative colouration." (P. 471.) In other words, 

 it is suggested that the present unicolorous hues of such organisms as green 

 birds and caterpillars, isabelline desert animals and flat fishes, &c, are pre- 

 ferably to be explained on the ground that they are survivals of an assimi- 

 lative colouring which was acquired in early geological times, its persistence 

 being due not to the direct action of natural selection, but to the fact that 

 this colouring happened, quite by chance, to be of vital importance to the 

 animals.* 



Now, apart from other objections, the acceptance of such au hypothesis 

 appears to me to land us at once upon the horns of a dilemma. Either we 

 have to believe that these unicolorous animals have existed as we now see 

 them since the " early stages of animal life," or we have to assume that these 

 organisms, with their numerous ancestry, right back to the low generalised 

 form from which they sprung in "remote antiquity," must have existed 

 through countless ages of time and innumerable geological and climatic 

 changes in an unchanging environment to which their primaeval assi- 

 milative colouring chanced to be so well adapted, that natural selection 

 has been quite unable to affect them in that respect throughout the entire 

 period ; although, be it noted, their structure has undoubtedly undergone, 

 in most cases, very considerable modification. 



This conclusion is to me almost as untenable as the previous one; and, 

 as it is difficult to perceive in what other way the present phenomena of 

 colour can be explained upon the suggestion of the survival of ancestral 

 assimilative colouring, it seems to me that this hypothesis must fall to the 

 ground. The fundamental error of the suggestion appears to lie in the fact 

 that the development of colour has been regarded in a purely abstract light, 

 and not in connection with the development of any particular animal or group 

 of animals, as must be done in order to arrive at any reliable results. 



* The inference, " quite by chance to be of vital importance to the 

 animals," is not to be found in the pages criticized. — Ed. 



