52 J. M. ESSENBERG. 



ventral portion of the ovary. As that part of the ovary has not 

 as yet fused dorsally, the extending cord is V-shaped with the apex 

 ventrally (Fig. 6). This portion of the duct grows posteriorly on 

 the dorsal edge of the mesentery until it reaches and fuses with 

 its posterior member. The mesovarium thickens and flattens above 

 the posterior portion of the ovary and finally comes in contact with 

 the open end of the V to fuse and thus form the lumen in the 

 oviduct from the anterior primorclium (Figs. 6-8). 



That the duct starts to grow from two sources was first noticed 

 in an abnormality in which the, two growing tips overlapped with 

 the urinary bladder between. In normal development the duct 

 forms ventral to the urinary system, but in the case in question the 

 anterior part of the duct had pushed above the urinary bladder, 

 while that from the posterior end was in the normal path. The 

 overlapping was for a considerable distance. This stimulated 

 closer study, and it was found that at the time when cords are 

 formed at both ends no traces of such exist centrally (Fig. 14), 

 nothing but a single layer of peritoneal lining. Further it was 

 ascertained that by far the larger part of the duct comes from the 

 posterior source. 



In the primordial germ cells of the indifferent stage there is only 

 one nucleolus with irregular, generally spherical contour. It al- 

 ways stains with chromatin dyes. Later its contour becomes per- 

 fectly regular and it enlarges. Still later two nucleoli are usually 

 found, though as many as six may occur. In the ova of medium 

 size (.272 mm.) the nucleoli are conspicuous bodies and may meas- 

 ure lO/x in diameter. A body similar to the nucleolus in stain and 

 size was noticed in the cytoplasm. At first it was taken for a 

 centrosome, but as it showed no structure whatever the first hy- 

 pothesis had to be abandoned. Subsequently it was noticed that 

 one of the two nucleoli moves toward the nuclear membrane and 

 passes through it (Fig. 13). When it reaches the cytoplasm it 

 does not stay there, but moves toward the follicular wall (Fig. 16). 

 It is probable that the migrating nucleolus passes out of the fol- 

 licle, as it can be seen in all parts of the cytoplasm. The actual 

 process of passing through the follicular wall has not been noticed, 

 but bodies which answer to the description of the nucleolus are 

 occasionally encountered between the follicles. Such migrating 



