1896.] Entomology. 679 
spiders, and according to Krause, in Cephalopods.—Journ. Royal 
Micros. Society. 
Weismann on Dimorphism in Butterflies.—For some time 
The Entomologist has been publishing a series of interesting articles by 
Dr. August Weismann on the Seasonal Dimorphism of Lepidoptera. 
The June number contains a recapitulation from which we take this 
extract: “Although I am far from considering the few experiments, 
which I could here put forward, as sufficient for reaching a decisive 
settlement of our opinions on seasonal dimorphism, yet I cannot forbear 
arranging them, provisionally at least, in reference to our general con- 
ceptions of the subject. When, in the year 1875, I first set about 
investigating the ways of this striking and yet so long neglected phe- 
nomenon, I assumed that it was to a certain extent obvious, that this 
kind of dimorphism was everywhere a direct result of the various 
direct influences of climate, principally of the temperature, as it effects 
in regular alternation the spring and the summer brood of many- 
brooded species. I had also well considered the other possibility, that 
dimorphism connected with the time of the year might also depend 
upon the indirect influence of the changing environment, i. e., that it 
might depend upon the adaptation to the varying environment of the 
butterfly according to the time of year.” 
I then said : “ It is not inconceivable in itself, that phenomena occur 
among the Lepidoptera analogous to the winter and summer clothing 
of Alpine and Arctic mammalia and birds, only with the difference, 
that the change in coloring does not arise in one and the same genera- 
tion, but alternately in different ones.” But, at that time the fact that 
the upper side of butterflies, which is usually not adaptive, can be very - 
variable just in summer and spring, sometimes more so than the 
adaptive under side, appeared to me to contradict this adaptation of 
seasonal dimorphism. Yet, it was the fact, that the one or the other 
seasonal form could be produced artificially by the operation of a higher 
or lower temperature, i. e. the stamp of the winter form might be im- 
pressed on the summer brood, and vice versa. I therefore concluded 
that it was the measure of heat which was acting during the pupal 
period which directly formed the species in one way or the other; and 
I felt the more justified in so doing, as the climatic varieties form a 
parallel to the seasonal forms, and as the former must, without doubt, 
be referred to the direct influence of climate, especially of temperature. 
Thus, for example, Chrysophanus phicas is seasonably dimorphic in 
Sardinia and at Naples; the summer form, which develops during the 
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