496 MONTGOMERY. [Vol. XV. 



we should expect to find the largest nucleoli in the smallest 

 cells and the smallest ones in the largest cells. Further, the 

 nucleolar substance cannot be regarded as a secretion of the 

 nucleus itself, since this would leave unexplained the peripheral 

 position which it at first occupies in the nucleus. Thus the 

 mode of origin of the nucleolus in these cells would seem to be 

 similar to that of the nucleoli in the ova of the nemerteans. 

 A final point may be noted : the nucleolus accepts the same 

 stains, though more intensely, than do the nutritive particles in 

 the cytoplasm ; accordingly, the substance of those bodies which 

 have been absorbed by the nucleus, and then by their fusion in 

 the nucleus produce the nucleolus, must have undergone either 

 a slight chemical or physical change within the nucleus. 



The largest mesenchym cells of the pseudoepithelia probably 

 represent the youngest stages of the ova, though in the single 

 individual of this species at my disposal no gonads were pres- 

 ent, so that I can bring no proof positive that this is the mode 

 of origin of the egg cells. In Carinclla it is from similar cells 

 that the genital products are derived, as I have previously 

 shown ('96). Coe ('95) described certain of the more mature 

 egg stages. 



In my earlier paper on these cells (/.f.) I termed all the 

 nuclear divisions of these cells "amitotic." But renewed study 

 of these elements shows that only the divisions of those cells 

 are amitotic (Figs. 316a and 317), from which the free mesen- 

 chym cells are produced. Whereas, in the nuclear divisions of 

 the cells of the pseudoepithelia from which the masses of larger 

 cells are derived I now find evidences of regularity in the 

 distribution of the chromatin, so that probably these divisions 

 are mitotic. However, in these small nuclear divisions it is 

 almost impossible to decide whether we have to do with mitoses 

 or with amitoses without the use of better lenses than those 

 which were at my disposal. 



21. Ganglion Cells of Nemerteans. 



I may here briefly mention the relations of the nucleoli in 

 these cells, and for other details refer to a previous contribution 

 of mine ('97). 



