No. 3.] MORPHOLOGY OF THE STENTORS. 495 



nuclei killed and stained with aceto-methyl-green and examined 

 in water or glycerine. The presence of a nuclear membrane 

 in the meganucleus of Infusoria was denied by Jickeli ('84), but 

 evidently on insufficient grounds. In the living condition the 

 membrane fits closely over the nuclear substance. 



In the meganucleus of all species of Stentor studied by me, 

 I have observed, in addition to the granular chromatin, a minute, 

 rather obscure chromatic network, which takes with all nuclear 

 dyes a decidedly deeper stain than the granular chromatin 

 (Figs. 8, 19-21, 60). This is evidently the structure seen and 

 figured by Carnoy ('84) in 5. polymorpJms, and believed by 

 him to be a much-involved chromatic filament. It has appeared 

 to me, on the other hand, that the meshes are "closed," and 

 that we have here to do with a chromatic "network." The 

 observational difficulties of solving the problem are so great 

 that it seems impossible to overcome them with our present 

 means of investigation. 



The chromatic network appears to be of wide occurrence in 

 the meganuclei of the Ciliata. It has been figured by 

 Schewiakoff ('89) for Holophrya discolor, Didmiimi balbianii, 

 and Dmophiya lieberkuehnii. Carnoy found it in Stentor and in 

 Vorticella. I have seen it very distinctly in Spirostonmm teres, 

 and less so in Paramecium caiidatiim. It is sometimes visible 

 even in the living nucleus of 5. ccsruletts, so that it cannot be 

 regarded as the effect of the reagent or of post-mortem change. 



The chromatic network always presents the same aspect of 

 delicate meshes composed of minute, wavy, granular-looking 

 threads. It is not peripheral, but, as focusing and sections 

 (Fig. 8, ingH.) show, runs all through the nucleus, and has the 

 same appearance from whatever direction it is seen. It is 

 evident, then, that the "network" is a web having three 

 dimensions. 



The network undergoes no visible change at time of division. 

 Constricted nuclei (Fig. 21) and moniliform nuclei in a state 

 of condensation (Fig. 8, vign.) do not reveal any modification 

 of it. I have never seen the least indication of a "striation" 

 or linear arrangement of threads in any constricted nucleus of 

 Stentor, such as Balbiani ('60), Biitschli ('76), Carnoy ('85), 



