184 EXTRACTS AND ABSTRACTS FROM FOREIGN JOURNALS. 



the super-acetate of alumina. There is, however, the same objection, 

 though to a greater extent, to the use of this fluid as to the salt water. 



ud. mixture of salt and water was* first recommended by Dr. Cook for 

 the same purpose, and has been known for more than twenty years. 

 There is a serious objection to the use of this solution for microsco- 

 pic preparations, owing to the development of a Confervoid vegetable, 

 as noticed by Mr. Bowerbank, at p. 159. 



Mr. J. T. Cooper some years since made some experiments wjth a 

 view to determine the best fluid for preserving vegetable coloured tis- 

 sues, such as some of the smaller Fungi, and found that salt and water, 

 to which acetic acid had been added, answered extremely well for this 

 purpose. This solution might probably answer for mounting dissec- 

 tions of vegetable structures. 



Kreosote and oil of copal, with the above, have likewise been tried, 

 but have not been generally used, probably on account of the difficulty 

 of obtaining the former free from colour, and the expense of both, com- 

 pared to the simple ones above described. 



antf ^flbatracts from dfawjjn journals. 

 [From Valentin's Repertorium, 1841.] 



Will on the Compound Eyes of Insects and Crustacea. Some excellent 

 researches, illustrated by good figures, have been published on this 

 subject, by Will of Leipsig. The author found the investigation 

 more convenient in subjects prepared in spirit than in fresh ones. The 

 facets of the cornea are hexangular in all insects, but in Crustacea 

 sometimes quadrangular, sometimes hexangular; quadrangular in 

 Palcemon serratus, Galathea strigosa, Astacus fluviatilis and marinus, 

 Palinurus locusta and Pasiphtea squinado ; hexangular in Squilla mantis, 

 Pagurus bernhardus, Portunus pubes and Ilia nucleus. The two eyes 

 occasionally vary in size. In the Libellula the facets in the upper 

 part of the eye are at least one-third larger than the rest. In the 

 Gryllotalpa vulgaris, those on the border of the cornea are about one- 

 third smaller than the others. The cornea is made up of prisms, or 

 truncated pyramids, corresponding in number to that of the facets. 

 Each pyramid presents, on a vertical section, oblique striae, usually more 

 than five, probably the edges of horny plates placed upon one another. 

 In Ranatra linearis, Naucoris cimicoides, Cicada orni, Tabanus bovinus, 

 there are found external and internal layers ; the former transparent, the 

 latter less so. The surfaces of both extremities of the corneal pyra- 

 mids are always convex, or at most level, but never concave. In Gala- 

 thea strigosa, Paloemon serratus, Astacus fluviatilis, and other Crustacea, 

 the external extremities of these pyramids are very slightly convex, the 

 internal even. In Cetonia aurata, Melolontha vulgaris, M. fullo, Calo- 

 soma sycophanta, Dytiscus marginalis, Staphlylinus erythropterus and 



