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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reinforced and possibly superseded by congenital variations 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. Memoiy 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 
px’ocess 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. Bay 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 1 And can 
we be sui’e that to any large extent the growth of instinct has 
been in their case actually screened by powers of functional 
accommodation 1 What we have ascertained on these points 
has been, I venture to say, largely or chiefly due to the 
