ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 441 



Composition of the Ova of Bombyx.* — Dr. Tichomirow Las 

 examined chemically the ova of Bomhyx. The weight of the ova was 

 not a constant quantity, 100 ova giving weights ranging from 0-2 to 

 ' 6 gr. The firm membrane of the ova has hitherto been universally 

 regarded as consisting of chitin. The easy solution, however, of this 

 membrane in solution of potash proves the inaccuracy of this assump- 

 tion. It consists, on the contrary, of a peculiar substance distin- 

 guishable from chitin, not only by its ready solubility in potash, but 

 also by a perceptible ingredient of sulphur. Chemically this sub- 

 stance has most relation to keratin, yet it contains less carbon than 

 the latter, and has therefore received a special name, " chorionin." 

 A comparison of the chemical composition of winter ova which had 

 undergone but a partial transformation with the Bomhyx ova developed 

 into caterpillars showed that in the latter the dry weight bad suffered 

 a little diminution, and that the ^lycogenous contents of the un- 

 developed eggs had almost entirely disappeared in the process of 

 development, but, on the other hand, that chitin, which was wanting 

 in the ova, was present in perceptible quantities in the caterjpillars ; 

 while the nitrogenous bases (nuclein probably) were also present in 

 greater quantity in the developed ova than in the undeveloped winter 

 ova. 



Influence of some Conditions on the Metamorphosis of the Blow- 

 fly.j — Mr, J. Davidson details six experiments made to ascertain the 

 effect of modifying conditions — heat, light, and darkness — on the 

 metamorphosis of the blow-fly. The result showed that darkness and 

 heat were favourable, and that light, and more especially the blue 

 rays, was unfavourable to the development of the larvae. Imagines 

 from pupse that had been kept in darkness were small, almost colour- 

 less, and translucent. An attempt to produce a vegetable feeding 

 variety failed. The larvee instinctively shun light. In conclusion 

 the author offers some observations on the necessity for heat and 

 darkness in development generally, and suggests that this may be an 

 inherited character. 



Head and Mouth of the Larva of Insects.^ — M. A. Barthelemy 

 briefly recapitulates the various forms of mouth in the larvae of 

 different insects, and shows that there exists in insects a general larval 

 form — the caterpillar — whose mouth resembles the appendages of 

 the Nauplius-form and the kindred appendages of the mouth in the 

 lower crustaceans, and that the study of the modifications of these 

 organs in the intermediary forms, nymj^haa and chrysalids, must pre- 

 cede that of the same organs in the perfect insects. 



Sensorial Organs of the Antennae of Ants.§ — Prof. A. Forel 

 gives a lengthy summary of the myrmecological discoveries in 1884, 

 and describes the organs of sense in the antennae of ants and some 

 other Hymenoptera, distinguishing three varieties of exterior organs. 



* Nature, xxxi. (1885) p. 620. (Proc. Berlin Pliysiol. Soc, 13th March.) 



t Journ. Anat. and Physiol., six. (1885) pp. 150-65. 



X Comptes Kendns, o. (1885) pp. 121-4. 



§ Bull, yoc, Vaudoise Sci. Nat., xx. (1885) pp. 316-80 (1 pi.). 



