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truly ' specific ' as the form, colour, and pattern with which 

 they are associated. The attitude of a stick-like Geometrid 

 larva, of a flower-like Mantis, or of a deceptively marked 

 spider, is as fairly attributable to natural selection as the 

 form, colour, and pattern. Such habits must also be asso- 

 ciated with specialisations of nervous function, with physio- 

 logical characters which find no expression in modern 

 systematics. It is obvious that diagnostic work, as at 

 present conducted, gives us only a restricted view of specific 

 characters." It is quite clear that my contention of the 

 development of species practically side by side under the 

 influence of a difference of constitution tending to the 

 isolation of a special form by any peculiar habit, such as 

 hybernation in a different stage from the parent stock, 

 appearance in the imaginal stage at a different time of 

 the year, becoming double instead of single brooded, 

 or vice versa, would be in the main agreed to by those 

 evolutionists of whom Professor Meldola may be considered 

 the exponent. We must, therefore, know the complete life- 

 habits of the animals we study, and to get a thorough notion 

 of the real nature of species we must depend upon the close 

 observation of the field naturalist, who will study such 

 species as comes under his notice, not from the standpoint 

 of specimens for a collection, but in their relations to their 

 environment as living creatures, a part of the great system 

 of nature into some niche of which each will be found to fit 

 exactly when we have paid the necessary attention to dis- 

 cover the character and nature of that niche. 



With regard to the question here discussed, it seems 

 practically certain that, when we come to consider the 

 change in pigmentation as one of the external means of 

 the differentiation of species, the external characters are 

 simply the result of changed physiological conditions or 

 functions performed under different conditions ; and it is 

 quite possible that in a greater or less degree the forms 

 exhibited in cases of seasonal dimorphism are simply the 

 outcome of development of the two extreme points of 

 physiological variability to which a species has been able to 

 reach in response to climatic influences, and which are pro- 

 duced under the stimulus of such influences, the seasonal 

 forms being the manifestation of two distinct kinds of 

 physiological activity, set in motion by the necessary 

 cHmatic influences, rather than the direct result of the 

 climatic influences themselves. In the same way, results 

 often attributed to food, temperature, &c., may be in reality 



