26 JOHNS HOPKINS UNIVEESITY MORPHOLOGICAL MONOGRAPHS. 



between the visceral follicle cells are almost invisible, and their nuclei 

 are elongated in radial lines, and are irregularly pear-shaped, with an 

 aggregation of a substance, which stains very deeply, at the central end. 

 These elongated nuclei are often arranged in pairs, the two members of 

 the pair lying in the same radius, and many of them are in the act of 

 dividing into an inner and an outer portion. In Fig. 2, which is from the 

 somewhat older embryo which is shown in Plate XI, Fig. 3, a is a folli- 

 cular nucleus which is about to divide, b is one in the act of division, 

 and c is one which is separated into two daughter nuclei, of which the 

 inner one has migrated inwards to a considerable distance towards the 

 center of the embryo. In their migration some of these nuclei push 

 their way in to the substance of the blastomeres, and in Fig. 1 one is 

 shown in the act of penetrating its outer wall. Some of the bodies inside 

 the blastomeres are sharply defined, and these agree with the follicle 

 nuclei in size, in their color in stained specimens, and in the arrange- 

 ment of their chromatin ; and the study of sections at this and subsequent 

 stages proves that the less sharply defined bodies are follicle nuclei in 

 process of degeneration, and that the blastomeres are nourished by 

 migratory nuclei from the visceral layer of follicle cells. The space 

 between the blastomeres is also filled with these nuclei in all stages of 

 degeneration and with the granules which have come from their disinte- 

 gration. 



The multiplication of the blastomeres goes on slowly, and while they 

 gradually become smaller and more numerous, as shown in Figs. 3, 4, 5, 

 6 and 8, they are seldom found in the act of division. The material 

 which is assimilated by the blastomeres from the migratory follicular 

 nuclei, seems for some time to be converted into chromatin ; for while the 

 protoplasm of the blastomeres continues transparent, as shown in Figs. 

 2, 3 and 4, the chromatin of these nuclei increases in amount and forms 

 a sharply defined reticulum with a large central nucleolus, and a number 

 of smaller nucleoli around the periphery and in the meshes of the net- 

 work. The nuclei of the follicular cells, on the other hand, become vesi- 

 cular and transparent through repeated division, and their chromatin 

 becomes more and more scanty, while they continue to divide so rapidly 

 that they show a well-marked arrangement in pairs, as is shown in Fig. 

 3 and in the following figures. As the blastomeres continue to multiply 

 they gradually become very granular, as is shown in Figs. 5, 6 and 8, and 

 even after they have become nearly as small as the follicle cells, they are 

 easily distinguishable by their large nucleoli and conspicuous network, 



