ZOOLOGY AND EOT AN Y^ MICROSCOPY, ETC. 141 



Some objects may be fixed by heating them on the slide up to near 

 boiling-point, instead of using osmic acid. 



Preparation of Fungi.* — Dr. G. Istvanf& describes the various 

 modes of preparing fungi for microscopical examination. Preservation 

 in alcohol of 60 per cent, serves for smaller dry fungi, Gasteromycetes 

 (except such as can be preserved dry), most Ascomycetes, the colourless 

 Agaricini and Polyporese (but not the Boleti), and the Hydnei, Clavariei, 

 Thelephorei, and Tremellini. For the softer Hymenomycetes, alcohol 

 cannot be used. A solution of salt answers better for these ; but, with 

 many, only preserves them for a comparatively short time. Pure sodium 

 chloride should be dissolved in freshly boiled water till saturated, then 

 filtered and used at once. The fungus should be completely immersed 

 in it. This answers for many Hymenomycetes and Pezizse. Other 

 preserving fluids are corrosive sublimate of ' 1 per cent., boracic acid of 

 2 per cent,, and a mixture of acetic acid and glycerin. Fungi which are 

 preserved dry should always be washed with a • 5-1 • per cent, solu- 

 tion of corrosive sublimate, to destroy bacteria, larvae, &c. 



A convenient mode of making sections is also described, which should 

 be set, in the case of dark-spored species, by an alcoholic solution of 

 mastic or Canada-balsam ; in that of white-spored species with gelatin. 



Experiments with CMtin Solvents.! — The first experiments of Mr. 

 T. H. Morgan were made upon the eggs of the common cockroach, 

 and the selection turned out to be a most fortunate one. A great many 

 eggs are laid at one time, the whole number being surrounded by a stiff 

 chitinous coat, forming the so-called raft. The solvents used were the 

 hypochlorites of sodium and potassium, recommended by Dr. Looss in 

 1885. 



The most successful experiments on the cockroach's eggs were as 

 follows : — 



(1) The rafts were placed, in a fresh condition, in a weak solution of 

 eau de Labarraque (commercial fluid diluted with five or six times its 

 volume of water), and left until the chitinous envelope became soft and 

 transparent. The time varies ; if slightly warmed the time is less for 

 the warm solution, perhaps thirty minutes to one hour ; but one must go 

 more by the appearance of the chitin than by any definite time. If the 

 embryos are far advanced, they may now be removed from the envelope 

 one by one ; if still young, they had better be hardened and cut all 

 together. In both cases the eggs or embryos were next washed for a few 

 minutes in water, and then transferred for an hour to picro-sulphuric 

 acid, then as usual they are passed through the grades of alcohol, 70 per 

 cent., 80 per cent., 95 per cent. 



(2) To specimens which have been already hardened and preserved 

 the solvent may also be applied ; but in all cases where fresh material 

 is easily obtainable, it should immediately have its chitin softened and 

 then afterwards be preserved. Here the method is somewhat shorter, 

 since the substance has been previously hardened. From alcohol — 

 weak solution — they are put into the Labarraque and softened as 

 above, then passed through water and the alcohols, &c. 



* Bot. Centralbl., xxxv. (1888) pp. 343-5, 381-3, 394-5. 



t Stud. Biol. Lab. Johns Hopkins Univ., iv. (1888) p. 217, and Dr. 0. O. Whitman 

 in Amer. Natural., xxii. (1888) pp. 857-8. 



