Observations on the Nucleoli in the Cells of Hydra Fusca 289 



The cytoplasm of the endoderm cells appears to be almost structureless, 

 while there is genei-ally some structure to be seen in the ectoderm cells. 



Conclusions. 



The phenomenon here recorded seems to be something quite apart from 

 anything connected with cell division, whether mitotic or amitotic ; indeed, 

 it is only to be observed in cells that are in the vegetative condition. 

 The probability that it is intimately connected with, and dependent upon, 

 metabolism taking place in the nucleus, is very strong. While it is readily 

 observed in almost all the cells of the endoderm, it can be followed only to 

 a very limited extent in the cells of the ectoderm. The processes connected 

 with digestion are carried out by the cells of the endoderm. It would 

 therefore appear probable that the kind of metabolism in the nucleus that 

 is connected with digestion produces this phenomenon in a more striking- 

 manner, and more frequently, than is the case with the nuclear metabolism 

 taking place in the cells of the ectoderm. 



The rapid and very marked change in the staining reaction of the 

 nucleolus as it passes into the cytoplasm, suggests that some important 

 chemical or physical change takes place in the contents at this time. 

 Similar changes have been observed in the nucleoli of nerve-ganglion 

 cells.i 



It seems probable that the bodies here described as extruded nucleoli 

 have been frequently described as food particles. But we would point out 

 that the structures here dealt with are apparently in process of disintegration 

 at the periphery of the cell, become more defined in the neighbourhood of 

 the nucleus, and are found in their most definite form and in process of 

 active multiplication within the nucleus itself. 



1 Page May and Walker, luc. cit. 



DESCRIPTION OF PLATE. 



(In these drawings the cytoplasm of the endoderm cells is, for the sake of con- 

 venience, considerably diminished in size in proportion to the nuclei.) 



Fig. 1. Two endoderm cells showing the nucleoli budding. Some nucleoli are to 

 be seen in the cytoplasm. 



Fig. 2. Two endoderm cells showing the nucleoli budding. Several nucleoli 

 may be seen in the same cell. 



Fig. 3. Four ectoderm cells showing nucleoli budding. 



Fig. 4. An endoderm cell showing two large nucleoli and pseudopodial processes 

 in the nucleus, as well as several nucleoli in the cytoplasm. 



Fig. 5. Three endoderm cells showing nucleoli passing out of the nucleus. 

 In c a nucleolus which remains within the nucleus is seen to be as large as that 

 which is passing out. 



