( xcv ) 
obtained by our ex-President, Mr. Merrifield. So far they 
show, as many similar investigations by other naturalists 
have done, that it is possible by varying the external con¬ 
ditions to which a butterfly is exposed in its earlier stages, to 
induce a well-marked alteration in its final aspect. This is 
the first and obvious conclusion to be derived from these 
experiments. But Weismann, as I need hardly remind you, 
was not content to stop at this point. The fact "was un¬ 
deniable that warmth tended to produce in the northern form 
of the species an approach towards the darkened aspect of 
the southern race; and conversely, refrigeration brought 
about in the latter a tendency towards the familiar golden-red 
of German or English specimens. From this the further 
inference seemed clear that the difference in aspect of the 
two geographical races was a direct result of the temperature 
conditions to which they were respectively exposed during 
the course of their normal life-history. But it was further 
to be remarked that in neither series of experiments was the 
transformation complete. In each instance several members 
of the brood appeared to be unaffected, and in none did the 
artificially-produced lightening or darkening reach the same 
pitch of intensity as in the local races corresponding to the 
respective conditions of temperature. The most probable 
interpretation of this result seemed to be that, in Weismann’s 
words, the difference between the two geographical races 
originated in consequence of “ a gradual cumulative effect of 
the climate, the slight effects of one summer or winter having 
been transmitted and added to from generation to generation.” 
At this point we may imagine the neo-Lamai’ckian asking, 
“What further^proof can be required of the possibility of the 
transmission of acquired characters'?” It is admitted, he 
would say, that the difference between the northern C. j)hlaeas 
and the southern var. eleits is in some way or other the result 
of climatic conditions. It has also been shown that these 
conditions are only partially operative for a single generation. 
The effect is therefore cumulative. It has not been suggested 
in this case that the change is an adaptation ; no reason has 
been alleged why in the one instance the lighter and in the 
other the darker coloration should have been selected as being 
