No. I.] SPHYRANURA OSLERF. - 



that in which the specimen Hes, and the two are allowed to 

 mingle, with the result that in five or ten seconds death, but not 

 immediate fixation, ensues. The greater part of the fluid is now 

 drained away, and the worm straightened out gently with a 

 needle; when this is done — it should take but a few seconds, 

 as the flexibility of the specimen allows it to be arranged in 

 anyway — a second drop of the reagent is put on the worm 

 and allowed to stand for two or three minutes, after which the 

 form of the body is fixed. It can now be transferred to a 

 larger quantity of the reagent, where it must remain for thirty 

 minutes, and thereafter be passed through alcohols, gradually 

 increasing in strength from 30% to 90%. 



Lang's Planarian Fluid, as well as other solutions containing 

 corrosive sublimate, gave us less satisfactory results than 

 Flemming's fluid. With its use much greater shrinkage occurs 

 during fixation, as is especially well seen in the contents of the 

 ovary and testes ; but the preparations are of some value for 

 purposes of orientation, as the tissues generally are more 

 brilliantly stained than when Flemming's fluid has been 

 employed. Although this is the case, the cell-structure is, with 

 the exception of few tissues, much more easily studied in a 

 Flemming's fluid preparation. 



Solutions containing picric acid have not given preparations 

 offering any specially advantageous features; indeed it is diffi- 

 cult to avoid distortion, as well as shrinkage, with such media, 

 while Perenyi's fluid has the additional drawback of interfering 

 with the selective capacity of the cells for staining reagents. 



We have also used Delage's osmic carmine.^ It offers no 

 advantage over Flemming's fluid, when specimens hardened 

 by the latter are subsequently stained in alum-cochineal. This 

 procedure gives to the cytoplasm of ganglion-cells and their 

 processes a characteristic brownish-red hue, which throws 

 these cells into a very effective contrast with the sur- 

 rounding tissues. All nuclei take a reddish-purple stain 

 under this procedure, in which the cytoplasm rarely partici- 

 pates, and then only very slightly. 



No successful results were obtained in attempts to demon- 

 strate the nervous system with gold-chloride, all the tissues 

 having a strong tendency to take a violet tint with this reagent. 



'Arch, de zool. exper., IV., 120. 



