472 MONTGOMERY. [Vol. XV. 



which is nearest to the wall of the acinus, i.e., nearest to the 

 source of the food supply ; only then does it come to occupy a 

 central position within the cell, when the latter has attained its 

 maximum size and the thickness of the cell membrane shows 

 that the cell is assimilating little or no nourishment from 

 without. 1 



b. Somatic Cells. 



12. Ganglion Cells of Doto. 



(Plate 21, Figs. 36-49.) 



(I have studied those nerve cells which occur in the cerebral, 

 pleural, and pedal ganglia. Three kinds of these cells may be 

 readily distinguished and described in succession : (i) colossal 

 cells, which are found only in the cerebral ganglion; (2) cells of 

 medium size; and (3) small cells.) 



Colossal ganglion cells (^\^s,. 43-49). — The number of the nu- 

 cleoli in the nuclei of these cells varies from about six to thirteen ; 

 they are also variable in regard to the position which they 

 occupy in the nucleus, and though always excentrically placed 

 they never lie in contact with the nuclear membrane. Some- 

 times all the nucleoli in a given nucleus are of approximately 

 equal size, but as frequently one or two are several times larger 

 than any of the others. Where such larger nucleoli occur along 

 with a number of smaller ones, the former are usually vacuolar 

 in structure ; sometimes nearly all the nucleoli contain vacuoles, 

 in other cases none of them are vacuolar. Quite often the 

 nucleoli in a nucleus show slight differences in their staining 

 intensity, and one of them may stain quite differently from the 

 rest (Figs. 44 and 46). None of the nucleoli have limiting 

 membranes. No cases of nucleolar division were found, unless 

 those cases where two nucleoli lie near to one another may 

 represent the completion of such a division. 



Gattglion cells of medium size (Figs. 37—42). — In these the nu- 

 cleoli vary in number from one to four, two or three being the rule. 

 Those of the same nucleus frequently show differences in size 

 and form, as well as slight staining differences. In only one 



' For the observations of other writers on germinal spots in Hirudinea, cf. 

 O. Hertwig ('76), Leydig ('49), Whitman ('78), and Plainer ('89c). 



