WATORE 
97 
THURSDAY, JUNE 1, 1899. 
EVOLUTION WITHOUT SELECTION. 
Die Farbenevolution bet den Pieriden. Von M. C. 
Piepers. ‘“ Tijdschrift der Nederlandsche Dierkundige 
Vereenignig ; 2. Deel v.” Pp.70-289. (Leiden, 1898.) 
HE fact is becoming more and more widely recog- 
nised that the colours of animals, and especially of 
insects, afford excellent material for the investigation of 
dark places in the theory of evolution. As was long ago 
pointed out by Bates, and reiterated with increased 
emphasis by Wallace, the history of the modification of 
species is displayed to view on the wings of butterflies in 
a manner that is peculiarly legible and strikingly com- 
plete. There is, therefore, every justification for those 
students of evolution who, like Weismann, Eimer, 
Meldola, Poulton, Bateson, and several others, have de- 
voted much attention to the colour patterns of lepidop- 
terous insects, and have endeavoured with more or less 
success to use the facts made available by such detailed 
examination in the elucidation of the laws which govern 
the origin and development of species. 
The pamphlet named at the head of this article is the 
work of an author whose credentials entitle him at least 
to an attentive hearing. He has resided for nearly thirty 
years in the Malay Archipelago—chiefly in the island of 
Java; during the whole of which time, as he tells us, he 
has studied the entomology of that region, and has in 
particular continued to search for explanations of the 
various phenomena presented by the colours of its lepi- 
dopterous fauna. It might be expected, then, that he 
would be able to bring forward a mass of valuable 
material derived from such observations and experiments 
as can best be carried out amid the natural surroundings 
of tropical species, and would thus be in a position to 
afford real help towards the solution of questions like 
those of the value in the struggle for existence of mimetic 
or of warning colours, the importance of sexual selec- 
tion and the protective significance of seasonal modifica- 
tions. So far from this being the case, however, it must 
unfortunately be stated that he has done little or nothing 
to increase our knowledge in any of these or similar 
directions. 
The cause of his failure is not far to seek. Being, as 
he informs his readers, in most respects a follower of 
Eimer, though disagreeing with his master on certain 
points of detail, he looks for an explanation of organic 
evolution in the direction of “laws of growth,” uncon- 
trolled by any process of selection, but working out the 
transformation of species under the influence of external 
conditions which act upon organisms of varying degrees 
of susceptibility. The essence of his contention is the 
non-recognition of selection in any form as a factor in 
evolution, and he is apparently so sure of his position on 
4 priori grounds, that he has not thought it worth while 
to keep the selection hypothesis in -view even as a pro- 
visional basis for observation and experiment. This, 
the mparoy Weddos of his position, has had a most 
disastrous effect upon his work, both as an observer and 
asareasoner. It cannot be said that he has any new 
arguments of weight to bring forward ; the main part of 
NO. 1544, VOL. 60] 
his treatise is taken up with a laborious attempt to show 
that the course of colour-evolution in the Pierids (or 
“white” butterflies) has followed, and is following, a 
definite succession of stages, which continually occur in 
the same order. Starting from an original red, the 
process of colour-change in the Pierids, according to 
Piepers, is always tending to reach a final stage of white, 
which may be attained either by means of a gradual 
paling through orange and yellow, or through an inter- 
mediate condition of black. This inevitable tendency, 
arising from an internal impulse towards change in a 
definite direction, taken in conjunction with external 
influences which act chiefly by way of accelerating or 
retarding the process of change, and in relation with 
individual differences of susceptibility to stimulus, he 
believes to have been sufficient for the production of the 
assemblage of diverse forms which constitute the Pierid 
sub-family as at present existing. 
It is no doubt true that, speaking generally, there has 
been a fairly uniform tendency throughout this group of 
butterflies towards the replacement of an original dark 
by a white pigment. But this was not reserved for 
Piepers to discover, inasmuch as the view in question 
has been long ago advanced and supported by much 
more detailed evidence than that brought forward in the 
present treatise. Moreover, cases have been pointed 
out where, in consequence of mimetic adaptation or from 
other causes, the more usual process of change has been 
reversed or modified—a fact not noticed by Piepers, and 
not very favourable to his general view. But acquaint- 
ance with the work of his predecessors scarcely appears 
to be a strong point with the author, who frequently 
either ignores altogether, or dismisses in a curt sentence 
or two, results of other observers which certainly demand 
and deserve a careful comparison with his own. The 
part of his theory for which he really is entitled to claim 
originality, viz. that the primitive colour of Pierids was a 
uniform shade of red, seems to rest on extremely slender 
evidence. To any one who will take a comprehensive 
view of the whole sub-family, the conclusion from which 
Piepers does not shrink, viz. that the male of Apfpzas 
(Tachyris) zarinda most nearly represents in coloration 
the earliest form of Pierid, will appear to savour of the 
vreductio ad absurdum. WNithout going into the kind of 
detail which would here be out of place, we may safely 
assert that there is abundant evidence in favour of the 
contrary view ; and that in many cases, at all events, as 
in the genera MZylothris and Dismorphia, there is every 
reason to attribute the presence of much of the red or 
orange coloration rather to increased specialisation for a 
distinct purpose, viz. that of mimicry, than to reversion 
or survival. Hopkins’s researches on Pierine pigments 
are not unknown to Piepers, but the latter, perhaps 
wisely, refrains from attempting to reconcile them with 
his own conclusions. 
This brings us to what appears to us to be a serious 
offence on the part of the author against good taste and 
gsood manners in scientific controversy. Nothing but 
gratitude is due to him for the facts that he has recorded 
from his own experience ; most readers, indeed, will only 
wish that he had given us more of them. Nor can any 
one fairly complain of his absolute denial of the modifying 
influence of selection, even though he thereby puts him- 
1D 
