360 LOUIS MAX HICKERNELL. 



vitellarium. It never attains very great size. It consists of 

 from five to twelve intensely chromatic nuclei surrounded by a 

 glassy, homogeneous plasma. A section of a typical ovary is 

 shown in Fig. 10, Plate III. Both ovary and vitellarium are 

 surrounded by a delicate membrane. 



Zelinka does not figure a section of the ovary of Discopiis 

 containing more than four nuclei. This small number is fre- 

 quently observed in Philodina but the average number is slightly 

 larger. The clear, non-staining cytoplasmic portion of the 

 ovary seems to be similar in both forms but Zelinka does not 

 figure a membrane separating ovary and vitellarium. Whether 

 this last point was due to improper or insufficient staining is 

 hard to say but it seems that a limiting membrane should be 

 present. In Philodina a definite ovarian capsule can be easily 

 demonstrated in sections through the proper region of the 

 normal, free-swimming animals. 



Another point which leads me to believe that the staining 

 methods employed by Zelinka were insufficient to demonstrate 

 all structural details is the fact that he does not figure a nuclear 

 membrane in the nuclei of the vitellarium. The karyosome is 

 surrounded by a clear area as in Philodina but he figures no 

 limiting membrane about the entire structure. It is possible 

 that he thought the karyosome to represent the entire nucleus. 

 However this may be, there is, in all cases, in the vitellarium of 

 Philodina a definite nuclear membrane surrounding the clear, 

 outer zone of the nucleus. 



In cross-section the stomach-intestine (Plate III., Fig. 9, st) 

 shows as a thick-walled tube with a narrow lumen. From the 

 inner wall cilia project into the lumen while at the base of the 

 cilia are deeply staining granules, which Beauchamp, in other 

 rotifers, interprets as cross-sections of longitudinal muscle fibers. 

 My own observations lead me to believe that this interpretation 

 is correct. The stomach tissue is of a spongy consistency, the 

 ground substance appearing as closely packed vacuoles. No 

 cell walls can be demonstrated but nuclei are scattered at inter- 

 vals throughout its extent. The nucleus has a karyosome sur- 

 rounded by a homogeneous plasma which stains with acid dyes. 

 Scattered irregularly through the stomach tissue are large, deeply 



