308 
EIMER’)S EVOLUTION OF BUTTERFLIES.* 
TuHE criticism, by Professor Minot, of the 
second part of Himer’s work, ‘Artbildung 
und Verwandtschaft bei den Schmetterlingen,’ 
which appeared in Science at the beginning 
of last year (January 38, 1896, Vol. III., 
No. 53), gives me occasion to again explain 
Eimer’s evolutionary theory, which, so far as 
I can see from Minot’s article, has in many 
respects been misunderstood. It seems as 
though Minot were not well acquainted with 
Eimer’s earlier works on the markings of 
animals, works in which questions of evolu- 
tion were already discussed. And, as KHi- 
mer’s present views on this subject are 
chiefly founded on the results of these earlier 
works, it is easy to understand why many 
assertions which need these results for their 
proof, seem incomprehensible to Minot. 
Minot calls Eimer ‘an enthusiastic oppo- 
nent of Darwin’s theory of natural selec- 
tion.’ It is true that through his investi- 
gations on the markings of different groups 
of animals Kimer became more and more 
confirmed in his opinion that natural selec- 
tion was of no moment for the origin of 
species. This view is expressed in the 
‘ Butterflies,’ with the distinct reservation 
(see p. 68) that he acknowledges the effi- 
ciency of natural selection in preserving 
and intensifying such characters as have 
previously been developed by other agen- 
cies to such an extent as to become useful 
to the organism in question. Himer, then, 
occupies the same position that Mivart 
defended against Darwin (see ‘Origin of 
Species’, Germ. ed., 1876, p. 249 ff.) and he 
is a decided opponent of the teleological 
views spread by some of Darwin’s follow- 
ers rather than by the latter himself. 
According to Himer species originate by 
organic growth, a term first defined by him 
in his ‘ Origin of Species.’ In the constitu- 
*Die Artbildung und Verwandtschaft bei den 
Schmetterlingen, II. Teil., von Dr. G. H. Th. Eimer, 
und Dr. C. Fickert. Jena, G. Fischer, 1895. 
SCIENCE. 
[N.S. Vou. VI. No. 139. 
tional changes which organisms undergo 
during life in consequence of external in- 
fluences, such as climate, food, ete., he sees 
the first agents that cause the development 
of new characters. These changes first re- 
veal themselves as growth-phenomena. It 
is the struggle for existence that gives rise 
to selection from among these changes, 
that rejects or adopts. I must consider it 
a misrepresentation to call this view of the 
origin of species a bold hypothesis. It is 
merely the result of investigations which 
prove plainly that, in the more sensitive 
representatives of a species, external influ- 
ences can and do produce individual varia- 
tions, and that we find these as aberrations 
in contiguous districts and as species in 
those that are more distant. Himer first 
mentions this thesis in his work on ‘Das 
Variiren der Mauereidechse’* and makes it 
probable by his observations ; more striking 
proofs, however, are given in his work on 
the ‘ Evolution of Butterflies.’ Our native 
horadimorph butterflies, such as Vanessa 
levana and V. prorsa, Pieris bryoniae and 
napt, make it sufficiently obvious that ex- 
ternal influences are no indifferent factors 
in the formation of organisms. A variation 
of temperature to which the chrysalis is 
exposed produces, from the eges of one and 
the same species, butterflies which differ so 
much in their external structure that for a 
long time they were held to be separate 
species. Dorfmeister; and Weismann { 
* Eimer: Untersuchungen tiber das Variiren der 
Mauereidechse, ein Beitrag zur Theorie yon der Ent- 
stehung aus konstitutionellen Ursachen. Archiv. f. 
Naturgeschichte (und selbstindig). Berlin, Nicolai, 
1881. 
+ Dorfmeister: Uber die Einwirkung verschiedener 
wihrend der Entwicklungsperioden angewendeter 
Warmegrade auf die Farbung und Zeichnung der 
Schmetterlinge. Mitteilungen d. naturw. Vereins 
fiir Steiermark, 1864. 
{A. Weismann: Studien zur Descendenztheorie I. 
Uber den Saisondimorphismus d. Schmetterlinge, 
1875. 
