60 
I learn from the writings of Mr. W. H. Edwards, that the name of that 
butterfly is Chionobas Semidea (Say.) The description given by Mr. Seudder of its 
terrible struggle for existence, tends to arouse one’s interest in it, and-draws out 
one’s sympathy for it, as we contemplate the dreary and joyless life it is doomed 
to lead in its inclement home, so opposite to what is considered to be the typical 
life of a butterfly. Grant Allen’s conclusion is in perfect harmony with the 
theories prevailing on this subject, but there is another view that can be taken of 
it, which appears to me to be more in harmony with nature and observation, 
although it may spoil the romance, and give less play to the imagination ; and 
that is the one contained in the well-known principle of the power of environment 
to modify the external appearance of living forms, and their ability to accommo- 
date themselves to altered conditions. 
To illustrate the principle that I wish to apply in this case, I shall draw upon 
Mr. Edwards’s article on “ Pieris Bryoniz and its derivative forms,” to be found in 
Papilio, for June, 1881. Hesays: 
“The species, of which Bryoniz is one of the forms, is known as Napis 
having in Europe three manifestations, Bryonizw, Napi, and Napzez ; the last of 
these was until recently regarded as a distinct species.” Then quoting Dr. 
Weisman who says of Bryoniz: “This is to acertain extent the potential winter 
form of Napi. This type Bryoniz, in polar regions is the only form of 
Napi. Bryonie produces but one generation a year, and must, then, 
according to my theory, be regarded as the parent form of Napi.” He then states 
that in the Alps and Jura, Napi swarms everywhere, and crossing takes place, 
which causes variability in Bryoniz, but in Lapland Napi is never met with; so 
Bryoniz preserves its constancy, and concludes thus: “ Pieris Bryoniz should be 
elevated to the rank of a species, and ordinary winter and summer forms should 
be designated varieties Napi and Napee.” Then Mr. Edwards, after a description 
of the markings of the various forms, says, “There are therefore the three forms 
under which the species manifests itself in Europe, Bryonie, Napi, Naps ; of 
which Bryoniz may be considered the present form.” Now to get myself into 
harmony with nature, I have to reverse this order. We all know that 
butterflies are lovers of the sun; and that they are most numerous in kinds and 
examples in warm countries where they flourish most luxuriantly, the conditions 
being more congenial to them. Therefore the natural inference is, that butter- 
flies would first appear on this scene of life, in localities that were most favourable 
to them, and spread from these into those that were less so. We are all familiar 
with the restlessness of butterflies, and with what eagerness they will investi- 
gate every spot, seemingly with a determination to establish themselves there if 
possible ; they succeed if the conditions are at all favourable, and some of them 
succeed even where the conditions are most unlikely. Now as Bryoniz is a darker 
form than Napi, and Naps being lighter still, and taking the result of Mr. 
Edwards’s experiments in this direction as a clue to some of nature’s methods in 
this matter, which goes to show that cold has the effect of darkening the colour 
of some kinds, I infer that Napzee was the first to appear and to spread into a 
locality with a cold winter. This acting on the chrysalides, Napi appears as the 
spring form, and Naps as the summer one. As the distribution goes on it 
reaches a yet colder climate, where Nap disappears and Bryoniz is the spring 
form, with Napi as the summer one. Pushing yet onward it gets into a locality 
where the season is too short for two broods, when the single brooded Arctic and 
Alpine Bryoniz is alone to be found, and consequently constant, and there does 
not seem to be the slightest reason to doubt, that if every Bryonize was swept 
out of Europe in one season, their place would soon be filled from the warmer 
