56 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
and Weismann’s answer is that the warmth influences at the same time 
the wing-rudiments in the pupa and the germ-cells, and affects similar 
elements (determinants) in both. Merrifield’s experimental results here 
agree with Weismann’s. 
Another set of experiments, with Pieris napi, show that the deter- 
mination of summer or winter dress occurs directly after pupation ; that 
low temperature does not evoke the winter form if the exposure of 
the pupae is delayed until shortly before emergence, and that there 
are individuals which do not react to warmth. Experiments with Pieris 
napi var. bryonise showed in nine cases a puzzling occurrence of an 
ordinary napi form among the rest. 
A third set of experiments concerned Vanessa levana-prorsa. Just 
after pupation the influence of cold tends to evoke from the second 
generation (offspring of the April levana type) the levana form, but not 
in every case, as the tendency to the prorsa type is strong. In the third 
generation the great majority have a strong tendency to hibernation 
and the levana type, but some, even without high temperature, turn out of 
the prorsa type, and of the rest the majority may by the action of warmth 
on the fresh pupae, become more or less pure specimens of the prorsa 
type. Median forms, so-called porimse , always arise where a generation 
at the beginning of its pupa-period does not meet with the adequate 
temperature. Weismann’s present inclination is to regard the dimor- 
phism as adaptive, and not as the direct result of differences of tem- 
perature ; the temperature acts rather as the stimulus inducing the 
development of one of the two developmental Anlagen , than as a directly 
productive factor. 
The fourth set of experiments had Pararga egeria and var. meione 
for subject. The southern form meione , at 10°-14° C., becomes less 
bright in colour, though always brighter than egeria . A northern brood, 
at 25° C., was not visibly affected. This result confirms Weismann in 
the opinion that the influence of the climate is not direct, but germinal. 
Experiments on Vanessa cardui , made in order to test whether the 
influence of light could affect the formed pigmentation of the animal 
through its pupa-sheath, yielded a wholly negative result. So did 
similar experiments by Standfuss. 
With Vanessa urticse, Weismann showed the effect of cold and 
warmth in the pupa period in evoking darker or brighter colouring, but 
his results were much less emphatic than those of Reichenau and others. 
The influence of prolonged warming on a large number of hibernating 
pupae was tested, but in no case was there deviation from the normal 
marking or colouring. 
Weismann distinguishes direct seasonal dimorphism, referable to 
the direct action of variable environment, from adaptive seasonal dimor- 
phism, the outcome of a process of selection. He gives as an example 
of the former Chrysophanus phlseas , of the latter the caterpillar of Lycsena 
pseudargiolus, and perhaps Vanessa prorsa-levana. On the forms which 
illustrate adaptive dimorphism, the changes of temperature act only as 
Auslosungsreize. In P. napi both kinds are probably mixed. We have 
not space to give a full account of Weismann’s theoretical reflections, 
but the gist of the matter lies in the interpretation of environmental 
action as being oftenest a stimulus inducing the development of particular 
