310 
and Wiirtenberger’s* works and my own 
investigations of the shells of Molluscs 
have shown that other morphological 
characteristics apart from the markings 
produce regular changes in a definite 
direction. Taking this into considera- 
tion I do not consider it a ‘bold hypoth- 
esis’ on Himer’s part, when he believes 
he has found a confirmation of his law 
of markings in the case of butterflies, for 
“any hypothesis which explains various 
large and independent classes of facts rises 
to the rank of a well-grounded theory.” 
(See Darwin, Animals and Plants under 
Domestic. Vol. I., p. 8, 1868.) In the sys- 
tematic part of his two volumes on ‘ Butter- 
flies’ Eimer shows how seemingly insignifi- 
cant variations of the markings from the 
original form invariably develop into defi- 
nite characteristics of new aberrations and 
species, the changes being dependent upon 
physiological conditions. It can therefore 
not be asserted that butterflies are subject 
to the most multifarious liabilities to 
change. The markings of Segelfalter and of 
Swallow-tails can be reduced to one common 
scheme, which, as the illustrations show, is 
most simply represented by the markings 
of Papilio Podalirius. This scheme of mark- 
ings consists of eleven bands which extend 
over the wings in a fixed direction parallel 
to the axes of the body. They are called 
longitudinal bands and are always con- 
nected with certain veins of the wings. 
These eleven bands can undergo several 
variations. They can become broader 
and vanish altogether by means of lateral 
combination, become shorter in the direc- 
tion from the abdomen or head, and some- 
times quite disappear, or develop into single 
spots and form a transverse marking by 
Contrb. to Knowledge, 1889. The same: Phylogeny 
of an Acquired Characteristic. Proceedings of the 
Amer. Philosoph. Soc., Vol. XX XII., No. 143, 1895. 
*Wirtenberger: Studien tiber die Stammesge- 
schichte der Ammoniten, Leipzig, 1880. 
SCIENCE. 
[N.S. Vou. VI. No. 139. 
means of dark colored scales which show 
themselves on the transverse veins of the 
wings. In this way the Segelfalter, as well 
as the Swallow-tails, develop new forms, 
which, from showing only slight aberra- 
tions from the original form in the begin- 
ning of the évolutional series, differ ma- 
terially from it in the end. The same 
law which thus determines the evolution 
of the members of a group also determines 
that of the groups themselves. Each suc- 
ceeding one begins its development at a 
somewhat higher stage than its predecessor. 
Variations which are an exception in the 
lower groups become the rule in the higher 
ones. This is the reason why the repre- 
sentatives of the first groups of the Segel- 
falter ‘have markings very similar to the 
original form, while the third group con- 
tains butterflies which closely resemble the 
Swallow-tails.”’ 
The primitive Swallow-tails have attained 
a much higher degree of development than 
the primitive Segelfalter, but still it is not 
difficult to recognize that, although they 
are not immediately allied to the Segelfalter, 
yet their development follows the same 
direction. The Swallow-tails still possess 
indications of a separation of bands, which 
in the Segelfalter have coalesced. Further- 
more, fragments of markings which still 
occur in forms closely related to the Swallow- 
tails show that the development of their 
markings depends on the same conditions 
as those of the Segelfalter. It would lead me 
too far to describe in detail the directions of 
evolution which manifest themselves in the 
various groups. I will only mention that 
the tendency of the bands to broaden and 
to coalesce can be traced throughout the 
entire groups of Segelfalter and has pro- 
duced almost melanotic forms in the group 
of Asterias of the Swallow-tails. Further, 
the shortening of the bands from abdomen 
to head is characteristic of both Segelfalter 
and Swallow-tails. In both groups the 
