No. 2.] COMPARATIVE CYTOLOGJCAL STUDIES. 40 1 



little could be gained from a study of the living cells, in regard 

 to the minute structures with which we are chiefly engaged. 

 With only few exceptions {Rodalia and the two gregarines 

 examined) no cells were studied which had not been preserved 

 with at least three fixing reagents, and in some cases at least 

 half a dozen different fixatives were used. The preserving 

 reagents employed were the following : saturated solutions of 

 corrosive sublimate in distilled water (this being the only fluid 

 used hot), sat. sol. of the same in 50^ or 35^0 alcohol, Flem- 

 ming's stronger fluid (chromo-aceto-osmic acid), Hermann's 

 fluid (platinum chloride, acetic acid, osmic acid), sat. sol. of 

 picric acid in 50^ alcohol, Perenyi's fluid (chromo-nilric acid), 

 2/0 aqueous sol. of chromic acid, absolute alcohol, picro-nitro- 

 osmic acid. Those reagents which gave the best general results 

 were the fluids of Flemming and Hermann, and the alcoholic 

 solution of corrosive sublimate ; though the particular reagent 

 demanded depends both upon the object of study, as well as 

 upon the method of staining which is to follow. It is hardly 

 necessary to state that a structure found after the use of a 

 given fluid, but not apparent on material treated in a different 

 manner, was either regarded as an artefact, or doubts were 

 expressed as to its naturalness ; that is, only when a structure 

 was found to present itself to the eye in more or less the same 

 manner, after various methods of preservation had been 

 employed, have I regarded it as a natural appearance and not 

 as a result of the fixatives used. Thin serial sections were cut 

 of objects imbedded in paraffin, in the usual way. All staining 

 done was upon the sections on the slide, and the stains employed 

 were as follows : Ehrlich's or Delafield's haematoxylin followed 

 by eosin (sat. sol. in distilled water), nigrosine (a sat. sol. in water 

 diluted by six vols, water), sat. sol. of acid fuchsine in 50/0 alco- 

 hol, the triple stain of Ehrlich-Biondi-Heidenhain (as prepared 

 by Griibler, Leipzig), Flemming's triple stain (safranin, gentian 

 violet, and orange G.), Lyons blue (sat. sol. in 50^ alcohol), 

 gentian violet (sat. aqueous sol.), methylen blue (sat. aq. sol.), 

 brasilin (sat. sols, in water and in 35^ alcohol), Mayer's acid 

 carmine, cochineal (sat. sol. in yof) alcohol) ; while Grenacher's 

 borax carmine and alum carmine, Heidenhain's iron haematoxy- 



