70 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
a . Insecta. 
Coloration of Insects.* — Dr. Brunner von Wattenwyl has published 
a gorgeously illustrated essay on the coloration of insects, which has 
been translated by Mr. E. J. Bles. He discusses uniform and rainbow 
coloration, stripes, bands, and spots; the line of orientation which 
“ indicates the position assumed by the insect on receiving its colora- 
tion ; ” strokes and dots ; eye-spots ; spirals ; splash marks ; clouded 
markings ; stencil patterns ; erosion ; changes in patterns ; enlargement 
and diminution of spots and bands ; dislocation ; diminution of patterns ; 
changes due to adaptation ; staining of contiguous parts ; fading in 
covered parts ; colouring in relation to position ; and arbitrariness in 
coloration. 
The particular point of this essay is the evidence ( a ) that the colora- 
tion is frequently “ independent of the biology of the insect coloured, 
and in nowise connected with its structure ; ” (6) that a utilitarian in- 
terpretation cannot be verified throughout. “ The careless splashings, 
the defective stencil patterns, or the impairment of vision by a band laid 
over the eyes, and many other facts met with in the study of coloration, 
cannot be brought into relation with any purposeful tendency.” 
The translator points out the difficulty of weighing the possibilities 
of advantage and disadvantage, and notes that the Darwinian is quite 
prepared to find the occurrence of indifferent characters, or even of dis- 
advantageous characters in process of disappearance. He calls attention 
to the novelty of some of the facts which the author has brought 
together, and to the magnificence of the illustrations. 
Compound Eyes of Ephemerids.f — Herr Carl Zimmer prefaces his 
paper on this subject with an account of the division of the compound 
eyes into two parts which occurs in many different Arthropods. The 
phenomenon is seen in many Crustacea, especially Schizopods, and has 
been described by Chun. In Schizopods the eyes are divided into 
lateral and frontal eyes ; of these the lateral eyes retain their normal 
structure, while the frontal eyes show a great elongation of their ele- 
ments, and a diminution in amount of pigment. These modified eyes 
are adapted for the perception of movement, and for seeing in obscurity. 
The division of the eyes has also been noted in insects, but has not pre- 
viously been studied there in detail. The Ephemerids were chosen for 
the purpose, and especially the genus Cloe , of which several species 
were investigated. In this genus the eyes are normal in the female, but 
in the male are subdivided into small lateral eyes of the same type as 
the eyes of the female, and large prominent frontal eyes of peculiar 
structure. Among their chief peculiarities are the reduction of pigment, 
and the presence of a thick layer of a homogeneous fluid or jelly, lying 
between the outer (nuclear layer) and inner (rhabdome layer) of the 
retinulee. Such eyes, according to the views of Exner, are adapted for 
seeing in obscurity — they form Superpositionsbilder. . Further, the 
arrangement of the scanty pigment especially fits them for the percep- 
tion of movement. Their use is probably to enable the male to meet 
with the female, both sexes being of active flight, and mating taking 
* ‘Observations on the Coloration of Insects,’ by Brunner von Wattenwyl, 
translated by E. J. Bles, Leipzig, folio, 16 pp., 9 pis. 
t Zeitschr. wiss. Zool,, lxiii. (1897) pp. 236-62 (2 pis.). 
