DIFFEEENTIATION OP THE PROTOZOA. 365 



that anything like even a preliminary survey of the leading In- 

 fusorian types vfould occupy much time, even years : however, as 

 the results with some of those more easily manipulated were novel 

 and interesting in themselves, I thought it worth while to pub- 

 lish them as a short preliminary essay. 



After some trials I succeeded in obtaining sections in series of 

 Spirostomum. The animals were killed by osmic acid, or by 

 heating and afterwards fixing in Flemming's or Hermann's solu- 

 tion, in which they remained for twelve to eighteen hours, and 

 were then transferred to a tall tube, from which the supernatant 

 liquid was repeatedly decanted and replaced by distilled water for 

 some hours. After the last filling up the water was poured off and 

 alcohol added very gradually, in order to prevent contraction of the 

 delicate sarcode, until a 50-per-cent. solution was reached, in which 

 the Infusoria remained like a coarse precipitate at the bottom for 

 twelve to eighteen hours more. The strength of the spirit was 

 then increased until the whole was gradually replaced by absolute 

 alcohol. It made no difference as to the ultimate result whether 

 the objects were treated with cedar oil or chloroform and then 

 transferred to paraffin. So soon as the Infusoria had settled in 

 this last and it had been replenished two or three times, the larger 

 part of the fluid was poured ofl: and the remainder, with the In- 

 fusoria, shaken up slightly and cast in the usual manner. The 

 sections were cut in the usual way with a Minot microtome and 

 stained as required. 



Spirostoma treated in the above manner and stained with either 

 gentian-violet, Victoria blue, or orange, showed a splendid reti- 

 culum or vacuolation (quite invisible except in section) of the 

 whole protoplasmic body (sarcode) (PI. XXVII. figs. 2, 3, 4). The 

 meshes of this reticulum were finer round the nuclei and largest 

 between these structures and the periphery, where they died 

 down to a compact protoplasmic layer just within the actual outer 

 membrane. This layer undoubtedly corresponds to what Schiitt 

 described in Peridinium as the " Hautschicht." It is no less 

 obvious that the large vacuolations correspond to his " Saftkam- 

 mern" and the intervening reticulum to his " Fiillplasma." The 

 remarkable radial structures of G-reeff were not apparent, but 

 something, at least, suggestive of his " glanzende Punkte " [fine 

 refracting particles], in which this radial structure termiuated, are 

 seen underlying the apices of the longitudinal ridges (fig. 8, a). 



These sections appear to indicate the existence of denser tracts 



29* 



