226 BULLETIN 120, UNITED STATES NATIONAL MUSEUM. 



considerably thickened, showing darker in stained specimens. The 

 nuclei and the endosarc spherules are more crowded in this region, 

 and the ectosarc here is thin. The nuclei have their massive chro- 

 matin in the form of small, scattered particles. 



The differences between these Opalinas and the ordinary, more 

 orbicular O. ranarum (figs. 197, 198) seem at first sight to be specific, 



.« 











■r,:'fji 







>3): 



,-^- ^-^-'^W -^^^^Vf^-'^- ■■■■'■ 



v\\ 



Pig. 2iOO. — Opalina eanardm, form cinctoidea, X 460 diameters. Note the con- ,^ 



SIDERABLE CHROMATIN MASSES JUST INSIDE THE NUCLEAR MEMBRANES. FOE THE SAKE 

 OF CLEARNESS THE ENDOSPHERULES ARE OMITTED FROM MOST OF THE FIGURE. 



but in numerous infections from the same species of host one finds 

 these truncated forms along with the orbicular forms and a good 

 many individuals intermediate between the two. It seems there- 

 fore, that we have here but a diversity in form within the species. 

 The truncated individuals may be classed as Opaina ranarum form 

 truncata. 



