216 JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 



character and becomes merged, without any abrupt boundary, in the 

 germinal mass. The epithelial cells are elongated, with well-defined out- 

 lines, and the nuclei, which are a little smaller than those of the germ 

 cells, are finely granular, and more deeply stained than those of the 

 latter cells. When about to divide the nucleus becomes very large, 

 vesicular, with its chromatin gathered at the center, and these large 

 nuclei protrude from the plane of the others. All the rest of the genital 

 string consists, in this section, of a mass of embryonic cells, crowded 

 together and with a very thin layer of protoplasm between them, around 

 the transparent vesicular nuclei, each of which contains a few large 

 granules. The nuclei are a little larger than those of the epithelium, but 

 not very different in size from those of the surrounding tissues. There 

 are about 30 or 40 of them in each cross-section of this part of the stolon 

 at this stage, but it is difficult to count them, as many of those which are 

 shown in one section actually belong to the planes of other sections, and 

 are only grazed by the cut. 



Fig. 5 of Plate XXXI is a section through the germinal mass of the 

 same stolon, a little farther away from the root, and Tigs. 6, 7 and 8 are 

 successively farther away, and the last, Fig. 8, is near the tip of the 

 stolon. Fig. 9 is from a stolon a little older, and not quite so near the 

 tip. It will be seen from these figures, and from those in Plate XXI, 

 that the follicle covers all of the germinal mass, except a little of the 

 embryonic portion at the root of the stolon, and it will also be seen that 

 the cells which remain inside very quickly assume the characteristics of 

 eggs, and undergo no change, except a gradual increase in size, and in the 

 amount and distribution of the chromatin in the nucleus, and in its rapid 

 growth, until the eggs are fertilized. In the embryonic germinal mass, 

 Plate XVI, Fig. 7, and at the proximal end of one from a mature stolon, 

 Fig. 8, all the nuclei are capable of multiplication, and their chromatin is 

 scanty and consists of scattered granules, but while the peripheral cells 

 retain their power to multiply, the central cells lose it completely as soon 

 as the differentiation takes place, and from this time on they are defini- 

 tive ova. Their chromatin gradually takes the shape of a network with 

 a large central nucleolus, as is shown, from the base of an old stolon, in 

 Plate XLI, Fig. 9, and from the distal end of a young one, in the figures 

 on Plate XXXI. 



The follicle ultimately gives rise, as I have shown, to the testes of the 

 chain-salpa3, and to the egg capsules and the fertilizing ducts, which need 

 not be further traced here, and also to migrating follicle cells, which pass 



