522 MONTGOMERY. [Vol. XV. 



posited evenly throughout the nucleus, and not only at the 

 periphery. And his deductions are based in great part, as those 

 of most other investigators, on the study of maturation mitoses, 

 and he had not observed their first mode of origin, namely, their 

 origin in nuclei which are not in the prophases of mitosis, but 

 are only gradually becoming differentiated from somatic cells. 

 I have found no evidences in any cell that the nucleoli stand 

 in any genetic relation to the chromatin elements of the 

 nucleus ; and while the chromatin may derive substances from 

 the nucleoli, I am unacquainted with any observations which 

 show that the nucleoli derive any part of their substance from 

 the chromatin. In all the cases observed by me, the nu- 

 cleus appears to assimilate a substance or substances from the 

 cytoplasm, and after this substance has entered the nucleus it 

 apparently undergoes there a chemical change, and becomes 

 deposited on the inner surface of the nuclear membrane in the 

 form of masses of varying dimensions, which may be either 

 globular or irregular in shape, according as they are fluid or 

 viscid in consistency. In the case of the ova of the nemerteans 

 the substance taken up into the nucleus, and which there 

 becomes deposited in the form of nucleoli, is sometimes exactly 

 similar to the substance of the yolk-balls which lie in the cyto- 

 plasm ; in other cases it is probably similar to those metabolically 

 changed portions or inclusions of the cytoplasm, out of which 

 the yolk-balls are later differentiated. In Linens, indeed, the 

 yolk-balls may often be found halfway through the nuclear mem- 

 brane, and their appearance is exactly similar to that of the 

 nucleoli. In the mesenchym cells of Cerebratiilus the substance 

 of the nucleoli appears to be identical with that of the numer- 

 ous nutritive granules which are dispersed in the cytoplasm ; 

 the latter globules arise in the cytoplasm before the nucleolus 

 appears in the nucleus, and as soon as they become numerous 

 in the neighborhood of the nucleus, peripheral nucleoli begin to 

 appear in the latter. In the subcutical gland cells of Piscicola 

 the nucleolus, at the time of its most rapid growth, is apposed 

 to the nuclear membrane ; but when this period of volume- 

 increase has ceased, it is never found in this position. Further, 

 the paranucleoli of Rodalia appear first in contact with the 



