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no doubt serve in their day, as Professor Baldwin says, until 

 reinforced and possibly superseded by congenital variations 

 tending in the same direction. Memory thus established as 

 an inborn faculty, " the experimental use of memory images, 

 with corresponding success and utility, would be followed in 

 time by further variations, giving imagination and thought " 

 (Baldwin). 



In the higher animals we have no difficulty in perceiving 

 the co-existence of individual plasticity with the congenital 

 endowments of both mind and body. Instinct, one of these 

 congenital endowments, is not " lapsed intelligence," though 

 intelligence may be suffered to lapse if and when instinct is 

 ready to take its place. On the other hand, the reverse 

 process may and does occur. Instinct may fall away and 

 disappear before the encroachments of the increasing power 

 of individual accommodation, a power which is rooted in the 

 plasticity, and, to use Sir E. Ray Lankester's term, the 

 " educability," of the psychic organisation. This final stage 

 is naturally of most frequent occurrence in man. The relative 

 proportions of the two principles are regulated by natural 

 selection ; the best combination in regard to any given pur- 

 pose is the one that will win. 



Now the special application of these considerations to 

 Entomology I take to be this. The later stages of psycho- 

 physical development are comparatively accessible to our 

 observation. In the phylogenetic range of the higher verte- 

 brates, and the ontogenetic history of man, we have much 

 material for the study of the interplay of plasticity, educability 

 and power of individual accommodation, with the congenital 

 endowments of a relatively fixed and stable character, such as 

 instinct and the fundamental features of bodily structure. 

 But the earlier steps in the process are involved in much 

 obscurity. What do we really know, for example, of the 

 relative value of the parts played by psychic plasticity and 

 fixed instinct in the case of the lowest organisms ! And can 

 we be sure that to any large extent the growth of instinct has 

 been in their case actually screened by powers of functional 

 accommodation] What we have ascertained on these points 

 has been, I venture to say, largely or chiefly due to the 



