( ) 
evening. With regard to the specimens of L. sibylla, he should 
prefer to reserve his remarks for another occasion, but in the 
fine series of V. C-album he noticed many individuals as to which 
he might say at once that they seemed to bear out in a most 
interesting way the conclusions arrived at from former experi- 
ments, conducted both by Mr. Merrifield and by Dr. Standfuss, 
with other species. They showed evident marks of reversion, 
and these marks were again of so special a kind as to pre- 
clude the supposition that they were the direct result of changes 
of temperature. The most remarkable of these features, i.e., 
the well-developed condition of Series III., and the presence of 
blue points in the dark patches composing it, might be seen 
in a conspicuous form in the Chinese species Vanessa (Graj^ta) 
C-aurewn, which insect was for many reasons to be considered 
as one of the oldest surviving representatives of the Vanessid 
group. There could, then, be little doubt that in this 
instance, as in so many others, Mr. Merrifield had succeeded, 
by the introduction of altered conditions, in producing a 
reversion to a more ancestral form than that normally 
assumed by the species. The more these instances ac- 
cumulated, the more they seemed to him to strengthen the 
conclusion that the altered temperature-conditions were 
capable of acting as a stimulus to which each organism would 
respond according to its own pre-arranged constitution, and 
that it was only in comparatively rare cases that the new 
conditions operated as the causa efficiens of the change. (See 
Weismann's Eomanes' Lecture, 1894.) Even in such an 
instance as that of P. phlaas, it was, perhaps, too much to 
assume that the darkening of the scales was the direct result 
of a high temperature, for in other cases the same temperature- 
conditions led to the opposite result. If we pushed the matter 
further and proceeded to ask what was the nature of the 
pre-arrangement of material which enabled different species, 
during growth, to respond in a different manner to the same 
stimulus, and in many cases to respond by reverting to an 
earlier phylogenetic stage, we found ourselves at once on 
very debatable ground. It might, however, safely be borne in 
mind that under either of the two leading theories of heredity 
— the centripetal and centrifugal — it was perfectly con- 
ceivable that a competition took place during the growth of 
