534 Mimicry in Butterflies. [September, 
Among accessory-apparatus will be found that used by Messrs. 
W. H. Dallenger, and J. J. Drysdale, M. D., for the continuous 
observation of minute organisms. Those who read the Monthly 
Microscopical Journal, know what valuable results were obtained 
by its use. Would that the faculty to make use of instruments 
could be sold to the many purchasers. 
Microtomes, for cutting sections, are here in great variety and 
of all sizes. One with a marble basin larger than an ordinary 
-washing-basin. In some of the microtomes the knife is fixed and 
worked by a piece of mechanism like a lathe rest, such as that 
made by W. Apel, mechanician to the University of Göttingen. 
In another microtome the preparation is pressed forward by a 
micrometer screw, against a circular knife, set in motion by a 
lathe. This instrument is from the University of Prague. 
United States opticians and manufactures are totally unrepre- 
sented, which is much to be regretted, as in this ‘section they 
could have made an excellent show, — perhaps have carried off 
the palm. 
MIMICRY IN BUTTERFLIES EXPLAINED BY NATURAL 
SELECTION. 
RITZ MULLER, whose contributions to science are always 
worthy of special attention, endeavors in a recent German pe- 
riodical ! to show how the phenomena of mimicry in butterflies may 
be explained by the theory of Natural Selection. He bases his in- 
quiries upon the species of Leptalis found in southern Brazil, and 
although, as will appear below, he adduces reasons for believing 
the primitive stock to have been banded, and not like most of 
the family to which this genus belongs, simple white butterflies, 
he commences by showing how even such an extreme change 
could be wrought out by the survival of the fittest in the struggle 
for existence. 
“ Should,” he remarks, ‘the first unimportant variations from 
the original white color (of the Pierids) be useful only in attired 
ing to their possessors, at a little shorter distance, the attention 
of enemies flying carelessly overhead, they would become more 
and more useful, and cause their possessors to become continually 
more abundant in proportion to the type; they could eres 
serve as the basis for the gradual formation of a resemblance i 
to deceive even the sharp eyes of birds scanning the swarms $, 
Ithomias (the butterflies imitated by some Leptalids) for booty: 
1 Jenaische Zeitschrift fiir Naturwissenschaft, x. i., February, 1876. 
