444 SOME ZOOLOGICAL METHODS. 



cent, alcohol. This mass melts at about 60 C., penetrates 

 very rapidly, and solidifies very quickly. The sections should 

 be studied in glycerin. 



WRIGHT and MACALLUM (Journ. o/Morph., i, 1887, p. 1) find 

 that Sphyranura is for most purposes best fixed in liquid of 

 Flemming, and stained with alum-cochineal. 



Cercarise. SCHWAEZE (Zeit. f. wiss. ZooL, xliii, 1886, p. 45) 

 found that the only fixing agent that would preserve the his- 

 tological detail of these forms was cold saturated sublimate 

 solution warmed to 35 40 C. 



834. Turbellaria. Methyleo blue will in some cases be 

 found useful for the study of living specimens. 



Fixiug is difficult, arid generally unsatisfactory. 



For Ehabdoccela BRAUN (Zeit. f. wiss. Mik. y iii, 1886, p. 398) 

 proceeds as follows : For preparing entire animals, the spe- 

 cimens are got on to a slide, lightly flattened out with a cover, 

 and killed by running under the cover a mixture of three 

 parts of liquid of Lang with 1 per cent, osmic acid solution. 

 Other fixing media than that described were not satisfactory. 

 (BoHMia, however, commenting on this, says that for some of 

 the tissues, such as muscle and body parenchyma, nitric acid 

 and picro-sulphuric acid are very useful.) Sections may be 

 made by the usual paraffin method. 



DELAGE (Arcli. de ZooL exp. et gen., iv, 2, 1886 ; Zeit. f. wiss. Mik., iii, 

 2, 1886, p. 239) strongly recommends fixation (of Rhabdoccela Acrela) by the 

 osmium-carmine mixture, 167. Concentrated solution of sulphate of iron 

 is also an excellent fixing medium. The animals (Convoluta) die in it fully 

 extended. Liquid of Lang was not successful. 



For staining, he recommends either the osmium-carmine stain or impreg- 

 nation with gold (^ formic acid, two minutes ; 1 per cent, gold chloride, ten 

 minutes ; 2 per cent, formic acid, two or three days in the dark. It is well 

 to allow an excessive reduction to take place, and then lighten the stain by 

 means of 1 per cent, solution of cyanide of potassium). 



BOHMIG, commenting on the above, says that he has obtained very in- 

 structive images with Plagiostomidae fixed with sublimate and stained with 

 osmium-carmine. 



VON GRAFF (Die Organisation d. Turbellaria Accela, Leipzig, 

 1891; see Zeit. f. wiss. Mik., ix, 1, 1892, p. 76) has the fol- 

 lowing remarks : Chromo-aceto-osmic acid, followed by hae- 

 matoxylin, is good for the skin ; but even this method will not 

 afford a satisfactory preservation of the Rhabdites, which in 

 Acoela and Alloiocoela seem to be destroyed by swelling, whilst 



