ferent times of the year, the same
tract of ground (_a_, p. 113). From the mingling of the remains of the
Hyaena with those of the Reindeer and Hippopotamus in the Kirkdale
Cavern, he infers that the former preyed upon the Reindeer at one time
of the year, and on the Hippopotamus at another. He argues that in such
a manner might be explained the curious mixture of northern and southern
types which we find in the British pleistocene and in cave deposits.

Besides mammals, the only European animals which have received some
attention with a view to a study of their origin, are the Butterflies
and the Land-Snails. The entomologists who have taken up the problem
have in so far scarcely produced satisfactory results, as they all
seemed to be bound down to the hypothesis that practically all the
butterflies had been destroyed in Europe during the Glacial period.
Hofman, in his interesting little work, comes to the conclusion (p. 50),
that only in Greece and Spain could a small remnant of the butterflies
have survived the extreme rigours of climate. Greece was at that time
connected with Asia Minor, and Spain with North Africa; and the author
supposes that the semi-alien fauna inhabiting these tracts was mainly
responsible for the re-stocking of Southern Europe, but that the main
mass of our butterflies are post-glacial Siberian immigrants.

The work published by Messrs. Speyer deals only with the origin of the
Central European Butterflies. The period during which our European
species originated is not specified, but the authors believe that they
had their home either in Southern Russia or Central Asia. The fact that
the number of butterflies decreases very considerably as we proceed
north-westward in Europe appears to them to substantiate these views.
The apparent dislike evinced by butterflies to the damp Atlantic Coast
climate, they think, clearly indicates that they had originated in a dry
and more continental climate. The history of the North European
Butterflies and Moths has been carefully described by Mr. Petersen. He
adopts Hofman's theory as to the almost total extinction of the
Lepidoptera in Europe during the Glacial period. The chief immigration
to Europe after that period is, he thinks, Siberian.

At first there appeared species which belonged to a cold climate, and
which now live in elevated regions; then came forms suited to a milder
climate, which established themselves on the north-easterly slopes of
the Alp