ON PELOMYXA VIEIDIS. 369 



I have never seen these enlarged or containing anything like 

 a vacuole, a condition described by Greef for P. palustris; 

 nor have I ever seen anything in the protoplasm of P. viridis 

 resembling the " glanz-korper " of that author, or which might 

 be nucleoli escaped from a nucleus. 



I have frequently seen nuclei extruded from the protoplasm, 

 usually along with food debris or sand particles ; when so 

 extruded they remain for some time unacted upon by the 

 water, but in time the water seems to penetrate the nuclear 

 membrane, and the nucleoli exhibit Brownian movements, 

 and after some time come out into the water (fig. 9) ; but 

 although I have watched them for a long time I have not ob- 

 served them to undergo any change. 



I have been unable by the use of any preservative or stain- 

 ing process to make these nucleoli behave as does the single 

 nucleolus of so many Amoebae. This latter when treated with 

 osmic, chromic, or picric acids, and subsequently with picro- 

 carmine or alum carmine, stains deeply, while the nuclear 

 substance remains clear and transparent, almost unstained. 

 But when any one of these acids or even acetic acid is allowed 

 to act upon the nuclei of P. viridis, the nuclear substance 

 becomes opaque and granular, and the nucleoli disappear from 

 view on account of the now opaque character of the nuclear 

 substance. When stained, either by osmic acid or by picro- 

 carmine or alum carmine (preceded by fixing and hardening 

 reagents), and mounted in Canada balsam, they appear as 

 quite different bodies from the fresh nuclei. To such an 

 extent is this the case, that until I had actually watched a 

 single nucleus throughout the entire process I was not satis- 

 fied that the bodies which I had taken to be nuclei in the 

 fresh state were actually such bodies. What really happens 

 is, according to the views of Pfitzner and others, that the 

 chromatin substance, which is something distinct altogether 

 from the nucleoli, is brought into view by the staining process, 

 and obscures to a certain extent the nucleoli. The nucleus 

 stains diffusely all over, while very numerous minute granules 

 appear to stain more deeply. 



