ZOOLOGY AND BOTANY, MICROSCOPY.. ETC. 43 



Solidification of Silk Threads.* — Prof. R. Dubois has already 

 indicated that the solidification of the threads of silk, as they pass from 

 the silkworm's glands, is effected by a process analogous to the formation 

 of a blood-clot, but that the fixation of a certain quantity of free oxygen 

 is necessary. Further investigation has shown that the substance in the 

 silk-reservoirs contains a reducing principle, which explains the fixation 

 of oxygen. The glands strongly reduce osmic acid and nitrate of silver, 

 and a solution of their contents rapidly decolorises permanganate of pot- 

 ash. The chemical evidence shows that there is a globulin present in 

 abundance. 



Role of Insects, &c, as Carriers of Disease.f — Dr. G. H. F. Nuttall 

 makes a timely and valuable contribution to the literature of animal and 

 vegetable parasites, and their definitive and intermediary hosts, in a 

 critical and historical study of the part played by insects, arachnids, and 

 myriopods, as carriers of bacterial and parasitic diseases of man and 

 animals. Among the more important and interesting features of the 

 essay may be mentioned the evidence adduced to establish the connection 

 between flies and the spread of cholera, typhoid, and plague, the associa- 

 tion of Texas or tick-fever with Ixodes bovis, of Tsetse-fly disease with 

 Glossina morsitans and its recent visit to an infected animal, the subject 

 of filariosis, and the mosquito-malaria theory. The bibliographical 

 appendix is extensive, amounting to one-fifth of the monograph. 



Mosquitoes and Malaria.t — Prof. B. Grassi discusses the observa- 

 tions of Koch. He does not consider that they have made any contri- 

 bution to the aetiology of human malaria. It is also indicated that Ross's 

 discoveries are suggested by, and are confirmatory of, Grassi's previous 

 results. 



Development of Wings.§ — Messrs. J. H. Comstock and J. G. Needham 

 begin the fifth chapter of their elaborate account of insects' wings with a 

 discussion of the development. " It is well known that wings arise as 

 sac-like folds of the body-wall of the second and third thoracic segments. 

 These folds first appear at the point where the suture between the tergum 

 and the pleuron later developes. In most insects with incomplete meta- 

 morphosis they are so directly continuous with the tergum, and become 

 so solidly chitinised with it, that they have generally been interpreted 

 as outgrowths from its caudo-lateral margin." The general appearance 

 in insects with incomplete metamorphosis is that of two layers of very 

 elongate hypodermic cells, which meet in places and form the middle 

 membrane, and remain separat j in other places, forming the vein-cavities, 

 which usually contain tracheaa. The external and internal development 

 of wings in insecta with incomplete and with complete metamorphosis 

 agrees in some important respects. " In both cases the wings arise in 

 early life, and form a double plate-like fold of hypodermis, b3tween 

 whose layers trachea3 shortly penetrate. In the former the extension of 

 the wings is gradual and moderate, excepting at the time of transfor- 



* Ann. Soc. Linn. Lyon, xlv. (1899) pp. 76-7. 



t Johns Hopkins Hosp. Rep., viii. (1899) 154 pp. anil 3 pis. See also Lancet, 

 Sept. 16, 1899. 



\ Atti R. Accad. Lincei (Rend.), viii. (1S99) pp. 193-203, 223-30. Cf. this 

 Journal, 1899, p. 609. 



§ Amer. Nat., xxxiii. (1899) pp. 845-60 (9 fisrs.). Cf. this Journal, 1899, p. 482. 



