( Ixxv ) 



that diagnostic work, as at present conducted, gives us only 

 a restricted view of specific characters. Before pronouncing 

 upon the inutility of any character we should do well to bear 

 this fact in mind ; I put forward once again a plea for 

 studying the action of the living machine as a whole before 

 we decide that any single detail of structure or function is 

 useless. 



The correlation of habit with protective and aggressive 

 resemblance,* is to me one of the most striking illustrations 

 of the power of natural selection to utilise internal, in this 

 case psychological, characters.! I may remind you that on 

 the doctrine of the non-transmissibility of acquired charac- 

 ters, such habits are to be explained in the same way that we 

 account for useful structures, viz., by the action of selection 

 upon psychological congenital variations, and not by the 

 inheritance of a habit assumed by the individual dui-ing its 

 lifetime.;]: From this same point of view it may be remarked 

 in passing, that the whole subject of habit and instinct 



* Ann. Mag. Nat. Hist., 1878, p. loS. Also Lloyd Morgan, op.cit., p. 11, 

 et seq. 



+ This point was fully recognized by Darwin and Wallace in tLeir original 

 essays in 1858 (See Poulton's " Charles Darwin and Natural Selection," 

 pp. 78, 79). 



+ I use the word "psychological" in the general (Spencerian) sense of 

 indicating nervous function. Objections as to the improbability of such com- 

 plex correlations having arisen through the action of natural selection 

 because of the chances against the necessary co-adaptation of structures and 

 functions ever occurring iu individuals never appeared to me to be of any 

 weight. Underlying these objections there is the gi-atuitous assumi^tion that 

 the different components of the complex of characters have all been developed 

 simultaneously . But no evolutionist of the selection school has ever asserted 

 that this has been the mode of development of such characters. It is more 

 reasonable to believe that the various components have been added suc- 

 cessively in the order of time during the phylogeny, and that we now behold 

 the summing up of the results of a long series of superimposed iharacters, 

 some external and obvious, others internal and latent, but all of use by direct 

 or indirect adaptation (see Wallace's " Darwinism," p. 418 ; also the present 

 writer in "Nature," Vol. XLIII., pp. 410 and 557, and Vol. XLIV., 

 pp. 7 and 28). The late Dr. Romanes admits that if co-adaption can be 

 proved to result from a blending of adaptations, the difficulty would disappear 

 l" Darwin and after Darwin," Vol. XL, p. 68). Unfortunately the element 

 of time interposes itself as an obstacle to the experimental investigation of 

 such problems; more hopeful would appear to be the study of the_compani- 

 tiv^ ontogeny in allied groups of species. 



