90 REV. F. A. WALKER, D.D., F.L.S., 
out im extenso from these data, would, I suppose, be somewhat 
as follows:—The parents in each case are of the extreme 
white variety. One set of these, and likewise the larve that 
are their offspring in the following season, were fed on crab 
leaves, tending to produce and to perpetuate white, while the 
other set, and likewise their larvee, in succession were fed on 
small-leaved varieties of the willow, that similarly tend to- 
wards yellow (smull-leaved varieties having this tendency, 
and Salia Babylonica, the Hastern weeping willow, being the 
smallest leaved of them all). So that when a second genera- 
tion of larvae was fed on yellow producing food, the effect in 
the direction of white was much less manifest, although the 
same yellow producing food had no result whatever in the 
case of their progenitors, selected, as has been already 
noticed, from the extreme white variety. It is a highly 
interesting matter of observation, as it seems to me, how far, 
how long, and in how many individuals of a batch of cater- 
pillars, the selected and inherited white will prevail, when the 
food plant, season after season, is of a yellow tendency, or, to 
speak more correctly, the plant with which the larval sensory 
surface is brought into contact, as there is considerable evi- 
dence for believing that the influence of food upon larval 
colour does not consist in the eating, not in the comparatively 
simple phytophagous influence, but through the nervous 
system regulating the amounts and kinds of the vegetable 
pigments made use of, and that of the larval pigment 
deposited. I am of course open to correction, if I have 
unintentionally misrepresented the bearing of Mr. Poulton’s 
arguments in any particular while under the necessity of com- 
pressing the record of his experiments into small compass, 
and of only very partially and incompletely referring to the 
sundry and laborious investigations that one so talented and 
possessed of such power of research has conducted on behalf 
of science. 
Such work as he has so laudably commenced ought to be 
conducted by many individuals at the same time in reference 
to a great many species of insects, with a no less great 
variety of food plants, and through every succeeding season, 
for the compass of a whole lifetime, the consequent breeding 
and rearing, experimenting and observing and registering 
should be conducted,—and notably in the tropics, as much as 
if not more than at home,—if anything like an adequate 
generalisation, only attainable, as it seems to me, by the 
comparison of a multitude of instances, and through long 
process of time is to be arrived at; for after all there are 
