168 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Physiology of the Compound Eye.* — Herr A. Kiesel found a 
periodic displacement of pigment, first in one direction and then in 
the other, in the eyes of nocturnal Lepidoptera which ivere kept perma- 
nently in the dark. He believes that the phenomenon is the accom- 
paniment of the insect’s sleep. He suggests using the displacement of 
pigment as a test for discovering the range of light to which an insect 
is sensitive ; thus he finds that ultra-red rays are perceived by Plusia 
gamma. The second part of Kiesel’s paper seeks to explain how an 
insect requires but a small visual angle in order to perceive its sur- 
roundings and how it is thus saved from being blinded as it flies in the 
glare of the sun. 
Histology of Nervous System in Insects.f — Sig. R. Monti describes 
the nerve terminations in the muscles of Ortkoptera, Coleoptera, Lepi- 
doptera, and Hymenoptera,in larvae as well as adults. He used Ehrlich’s 
intra vitam methylen-blue method. In Ortkoptera the nerves generally 
show free terminations ; in larval Coleoptera the fibrils of the nerves end 
in clearly raised plates (collines of Doyere), and sometimes, as in the 
adults, in a cellular reticulum ; in larvae of Lepidoptera there are plates, 
in the adults the nerve-fibres give off lateral fibrils which ramify around 
the muscle-fibres and end in little knobs ; in the larva of Cimhex varia- 
bilis a terminal plate beneath the sarcolemma is very clearly seen. 
In the central nervous system of Gryllotalpa vulgaris , the nerve-cells 
seem all unipolar ; their prolongation may be traced into a nerve-fibre 
issuing from the ganglion, or it may be lost in ramifications. The granular 
substance of Leydig consists of a very fine coil of fibrils derived from 
the subdivision of the prolongations of the cells and from the subdivision 
of the fibres. But, in short, what Golgi has shown for Vertebrates seems 
also to be true of insects. 
Pigments of Pieridse.J — Mr. E. G. Hopkins publishes an abstract 
of a contribution to the study of excretory substances which function in 
ornament. The wing-scales of the white Pieridse are shown to contain 
uric acid, which substance bears the same relation to the scale as do the 
pigments in the coloured Pieridae, so that it practically functions as a 
white pigment. The yellow pigment found in the majority of the 
Pieridee is a derivative of uric acid. The yellow pigment may be arti- 
ficially produced by heating uric acid with water in sealed tubes at high 
temperatures, and the identity of the natural and artificial products may 
be demonstrated by the similarity of their spectrum. Mr. Hopkins 
believes that this yellow substance, which may be called lepidotic acid, 
together with a closely allied red substance, will account for all the 
chemical pigmentation of the wing-scales of the coloured Pieridae, though 
modifications may be produced by superadded optical effects. These 
uric acid derivatives, though universal in the Pieridae, are apparently 
confined to this group among the Bhopalocera. This fact leads to the 
interesting observation that where a Pierid mimics an insect belonging 
to another family, the pigments in the two cases are chemically quite 
distinct. The fact that the scale-pigments are really the normal excre- 
* SB. K. Akad. Wiss. Wien, ciii. (1894) pp. 97-139 (1 pi., 6 figs.). 
t Bend. R. 1st. Lomb., xxv. (1892, received Feb. 1895) pp. 533-50. 
X Proc. Roy. Soc., lvii. (1895) pp. 5 and 6. 
