No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 453 



they never lie in contact with the latter and are frequently 

 situated at some distance from it. Were they buds from the 

 large one, one would expect to find in them vacuoles such as 

 occur in the large nucleolus, but they never contain vacuoles. 

 In one nucleus (Fig. 207) I saw a disc-shaped mass apposed to 

 the inner surface of the nuclear membrane, which stained more 

 intensely than the chromatin. Such a peripheral mass may 

 be regarded as a substance taken up from the cytoplasm by 

 the nucleus, which, after passing through the nuclear mem- 

 brane, undergoes a chemical change to such an extent that it 

 stains with haematoxylin. The minute nucleoli may stand in 

 a genetic connection with such a mass of substance, that is, be 

 portions of a substance assimilated by the nucleus and after- 

 wards scattered through the latter. They might serve as 

 nourishment for the chromatin threads with which they are 

 often in contact. 



In seven nuclei out of about one hundred or more examined the 

 large nucleoli differed much from the ordinary type described 

 above. In one Q.gg pouch there was a smaller ovum apposed to 

 the animal pole of a larger one (Fig. 211); a normal nucleolus 

 was present in the nucleus of the smaller one. But in the larger 

 ovum two nuclei were present, in close contact with one another, 

 though separated by a membrane (coalesced nuclear membrane). 

 It is in each of these latter nuclei that an abnormal nucleolus 

 is present. Each of these nucleoli is finely granular, without 

 enclosed vacuoles, and stains faintly with haematoxylin ; the 

 one is regular in outline, but the other is jagged at one pole, 

 and a ring-shaped portion of its substance stains more deeply 

 than the remaining portion. In another ovum I also found two 

 nuclei, in each of which was a nucleolus similar to those just 

 described. In still another ovum two nuclei were found in 

 contact with each other, the nucleolus of one of which was 

 similar to those here described, but the nucleolus of the other 

 nucleus was intermediate in structure between these and the 

 ordinary type of nucleoli (Fig. 210). In only one case was 

 such an abnormal nucleolus present within an ovum contained 

 in a gonophore (Fig. 208) ; in the other six cases the abnormal 

 nucleoli were in ova of t^^ pouches. 



