616 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
An an example, the author cites the wonderful variability of insular 
shell-faunae such as those of Madeira and St. Helena Islands. The 
particular features likely to indicate local dynamic influence under 
the assumed conditions would be wrinkling, corrugation, shagreening on 
the surface, more or less rhythmical plaiting or wrinkling at the 
suture, loose coiling or dimpling of the nuclear coil at the vertex. 
The axis would exhibit a tendency to irregularity, corkscrew twist, or 
outward grooving, resulting in a tendency to form an angle or keel at 
the anterior edge of the pillar. The margin of the aperture would 
tend to thicken, and there would be a tendency to contraction at the full- 
grown aperture during or after hibernation. Of these characters, some 
are more likely than others to be selected as beneficial to the species, 
and these relate chiefly to general form and coloration. 
The author concludes with a summary of the land shell-fauna of the 
Galapagos Islands. A complete study of this archipelago should be 
made before occupation, especially by sheep, will render it impossible 
for ever to get complete data. 
Arthropoda. 
a. Insecta. 
Mouth-Parts of Insects.* — Mr. C. L. Marlatt has an abstract of a 
memoir on the mouth-parts of insects, with particular reference to 
Diptera and Hemiptera. He urges that it is incorrect to separate 
insects into the two groups of mandibulata and haustellata, since insects 
of all orders are, strictly speaking, mandibulate. Westwood’s division 
into biting and sucking forms is correct. The view which is generally 
held as to the construction of the mouth-organs appears to be correct, 
and there is said to be a total lack of evidence for the recent effort to 
show that the mouth-parts of the Diptera and Hemiptera are wholly 
maxillary. 
Pigments of Pieridae.j — Mr. F. Gowland Hopkins has published in 
full his memoir on the pigments of these insects, of which we gave a full 
account when the abstract of the paper was published.}; 
Mimicry in Hypolimnas.§ — Col. C. Swinhoe, after studying and 
thinking over the general theory of protective mimicry, conceived that 
the subject would be advanced by the special study of a small group of 
widespread mimetic species, throughout the different countries included 
in its range. While the Bolina group of Hypolimnas contains, according to 
systematists, a number of species, they can all be merged into two, and 
it was these that he selected for his purpose. He describes in detail 
the appearances of these widely spread forms, and comes to the conclu- 
sion that the facts afford the strongest support to the theory of mimicry 
as originally suggested by H. W. Bates; a variety of changes which 
occur are explained by this theory, and by no other yet propounded. 
Local changes may be explained by many theories, but that they should 
invariably be in the direction of a superficial resemblance to one butter- 
fly, and that one a specially defined species, is only to be explained by 
* Proc. Amer. Assoc. Advancement of Science, xliv. (1896) pp. 154 and 5. 
f Phil. Trans., B. 186 (1896) pp. 661-82. 
X See this Journal, 1895, p. 168. 
§ Journ. Linn. Soc., xxv. (1896) pp. 339-48 (3 pis.). 
