( Ixxiv ) 



might be ascribed to a savage who, never having seen a 

 watch in movement, was for the first time shown the silent 

 mechanism, and who, in complete ignorance of its mode of 

 action, declared his belief that this or that Avheel was useless. 

 Surely it is more scientific to use a reasonable hypothesis as 

 a weapon instigating inquiry into all possible uses of specific 

 characters than to put one's own negative conclusions in the 

 place of positive knowledge. 



To realise fully how much of importance may be dropped 

 out of consideration by paying exclusive attention to the 

 external characters of cabinet specimens, it is only necessary 

 to recall the numerous cases of mimicry and protective and 

 aggressive resemblance which are so commonly met with 

 among insects. I take it for granted that the characters 

 which contribute to these disguises are useful. If utility is 

 not obvious in all such instances, then nothing in the realm 

 of organic nature will bear the interpretation of utility. 

 Would any naturalist accept as an explanation of these 

 phenomena the statement that there existed a natural force 

 tending to mould organisms into a resemblance to their en- 

 vironment ? We might as well say that the laws of planetary 

 motion were brought about by the intervention of guiding 

 spirits, as was the belief of pre-Newtonian astronomers. 

 Now these adaptive and demonstrably useful characters are 

 surely " specific," whether the systematist attaches much or 

 little weight to them in his diagnoses. Moreover, the dis- 

 guise is enhanced and, in many cases, is only really effective 

 when combined with certain habits which are not, and cannot 

 be taken into consideration in ordinary diagnostic work. 

 Nevertheless, such habits are as truly " specific " as the form, 

 colour, and pattern with which they are associated. The 

 attitude of a stick-like Geometer 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 associated with specialisa- 

 tions of nervous function — with psychological characters which 

 find no expression in modern systematics.* It is obvious 



* For remarks on this subject see Chap. I. of Lloyd Morgan's recent 

 vvork on " Habit and Instinct.'' 



