594 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Two specimens were taken, one killed in bright sunshine, the other in 
the dark. - The author gives figures showing (1) a section of the eye of 
Hydrophilus piceus taken in the dark, in which the crystalline cones 
may be seen to be thickly coated with pigment, but to have ends free, 
and the space between them and the retina clear ; (2) a section of the 
illuminated eye has the spaces between the cones poor in pigment. 
Other figures represent a crystalline cone of Dyticus marginalis. 
By the effect of the pigment the summation image, instead of consisting 
of thirty or more images, is made up of only a few, It may be even so 
far reduced that each point of the object is depicted only by one facet. 
Fig. 71 shows a number of facets of a Ctenophora Jlaveolata, in which 
the retinula, consisting of seven cells, is separated from the dioptric 
part of the facet by pigment in such a way that light can only reach the 
retinula through a narrow opening. Supposing the dioptric apparatus 
of each facet to act, as in the Lampyris-e ye, as an astronomical telescope, 
there results an erect image as seen from the figure. 
As regards the accommodation of the Lampyris-eye, the forward 
displacement of the image corresponding to the approach of the object 
was in one case measured. It amounted to 0*092 mm., when the object 
was moved from a distance of 810 mm. to that of 1 *2 mm. 
Secretion of Silk in Bombyx mori.* — M. B. Dubois discusses the 
mode of coagulation of the silk-secretion. He comes to the conclusion 
that it is not comparable to that caused in white of egg either by alcohol 
or heat, but to the coagulation of blood or muscular fluid. A sort of 
serum or sericigenous plasma maybe easily obtained by maceratiDg silk- 
glands, for two or three days in a cool place, with distilled water, water 
containing 4 per cent, of salt, or, still better, with a 15 per cent, solution 
of carbonate of potash. This serum will give a coagulum without the 
addition of any reagent, and, when still moist, has the ductility and 
elasticity of freshly-formed silk, but it soon loses its property of being 
drawn out into threads. As with the coagulation of blood, the formation 
of silk-clot is favoured by oxygen. 
Parthenogenesis of the Ova of Bombyx.f — Sig. E. Verson found 
that the development of unfertilized eggs of the silkmoth stopped, 
without power of further progress, after twenty-eight days, and that at a 
stage which corresponded approximately to the state of fertilized eggs 
three days after deposition. He also criticizes the methods and results 
of previous investigators of this case of parthenogenesis. 
Anatomy of Sesia tipuliformis and Trochilimn apiforme.j: — Prof. 
E. K. Brandt points out that the anatomy of the Clear-wings is par- 
ticularly interesting, as these moths exhibit obvious mimicry. It is 
probable that the Clear-wings are ancient forms which have lately 
acquired a special adaptation to (or mimicry of) other flower-frequenting 
Insects. The proboscis of Sesia tipulijormis is moderately developed, 
but very weakly constructed ; the nervous system is arrested in develop- 
* Comptes Rendus, cxi. (1890) pp. 206-7. 
f Bull. Soc. Entomol. Ital., xxi. (1890) pp. 118-23. 
J Horse Soc. Entomol. Ross., xxxii. (1889) pp. 41-9. See Ann. and Mag. Nat. 
Hist., vi. (1890) pp. 285-90. 
