474 CHAPTKR XXXVL 



914. Ctenophora : Fixation. --The small forms are very easily 

 prepared by means of osmic acid. For the large forms see 

 Lo BIANCO, loc. cit., p. 457. He uses his copper sulphate 

 mixture, 910. 



SAMASSA makes sections by the double-imbedding method, 

 see Arch. mik. Anat., xl, 1892, p. 157. 



Pur if era. 



915. Spoiigiae : Fixation. --The smaller forms can be fairly 

 well fixed by the usual reagents, osmic acid being one of the 

 best. For the larger forms absolute alcohol is apparently 

 the best. If any watery fluid be preferred, care should at 

 all events be taken to get the sponges into strong alcohol as 

 soon as possible after fixation, on account of the rapidity 

 with which maceration sets in in watery fluids. FIEDLER 

 (Zeit. iciss. ZooL, xlvii, 1888, p. 87) has been using (for 

 Spongillajj besides absolute alcohol, an alcoholic sublimate 

 solution and the liquids of Kleinenberg and Flemming. 



Staining.- -To avoid maceration, I hold that alcoholic 

 stains should be alone employed, and I recommend Mayer's 

 tincture of cochineal, 235. YON LENDENFELD (Zeit. wiss. 

 Mik., xi, 1894, p. 22) uses aqueous solutions of Congo red and 

 anilin blue for the coloration of collar-cells. 



i 



MINCHIN (Quart. Journ. Mic. Sci., xl, 1898, p. 569) stains 

 spicula sheaths with Freeborn's picro-nigrosin, 681. 



ROUSSEAU (Ann. Sue. Bvltj. Mic., xxiv, 1899, p. 51) stains 

 in nigrosin, picro-nigrosin, or indulin, or HAYEK'S picro- 

 magnesia carmine. 



For intra-vitam staining, see LOISEL, 208 ante, p. 138. 



For silvering, see 356. 



Sectioning. - - Calcareous sponges may be decalcified in 

 alcohol, acidified with hydrochloric or nitric acid, and then 

 imbedded in the usual way. Siliceous sponges may be 

 desilicified, 574. 



For ROUSSEAU'S methods, see 574. VOSMAER and PEKEL- 

 HAKING decalcify with a solution of picric acid in absolute 

 alcohol' (see Zeit. icifs. Mik., xv, 1899, p. 462). 



See also Johnston e-Lavis and Vosmaer, 179. 



Preparation of Hard Paits. Siliceous spicules are easily 

 cleaned by treating them on a slide with hot concentrated 



