No. 3-] MORPHOLOGY OF THE STENTORS. 499 



greater bulk of the deeply-staining meganucleus. It is use- 

 less to search for them until the Stentor has been cut into 

 thin sections or the meganucleus isolated. The serial-section 

 method is the most satisfactory, and the best stains I have 

 tried are Czokor's alum cochineal and borax carmine. The 

 micronuclei always lie close to the meganucleus, as usual 

 among Infusoria (Figs. 19, men., 25), but not always absolutely 

 in contact with it. While sometimes seen with great distinct- 

 ness, I have not been able to make them out in many speci- 

 mens, although prepared in the same manner. They are 

 peculiarly difficult to find in individuals that have entered upon 

 fission, owing to the fact that they swell and become almost 

 unstainable at time of their division. 



The number of micronuclei in Stentor is larger than in any 

 other Infusoria, so far as known, and has been greatly under- 

 stated by Maupas '('83, p. 661), who mentions as the highest 

 number, 28 for S. roeselii. In serial sections of a Blue 

 Stentor in which the micronuclei were unusually distinct, I 

 have counted 66, and in another instance, 54. The absence of 

 numerical agreement which Maupas ('83, p. 661) found the 

 micronuclei of Spirostonium ambiguum to possess, with refer- 

 ence to the nodes of the meganucleus, also prevails in Stentor. 

 While often only one micronucleus may be found adherent to 

 a node (Fig. 19, men), there are sometimes as many as seven 

 or eight. 



The micronuclei of 6". cczruleiis do not differ materially from 

 those of other Infusoria. They are spherical, highly-refractive, 

 deeply-staining bodies measuring i.5ju.-2/a in diameter, appar- 

 ently homogeneous and composed wholly of chromatin (Fig. 5 5). 

 They are so minute and dense that I have been unable to 

 discern a nuclear membrane in the resting state, but one is 

 visible when the micronuclei are enlarged at time of fission or 

 conjugation (Figs. 48, 56). 



Hitherto, micronuclei have not been observed in the Stentors 

 having simple meganuclei. I have found them in 6". ignetis, 

 adherent in considerable numbers to the meganuclei (Fig. 25), 

 and also in S. pyriformis . They are even smaller than the mi- 

 cronuclei of the Blue Stentor, measuring only Hi. in diameter. 



