92 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



ing nuclei in various stages of chromatolytic degeneration, while 

 outside the vesicles are other nuclei, which, though staining faintly, 

 appear to be in a healthy condition. It seems, then, that some of the 

 cells of the corpus luteum retain their vitality and digest their neigh- 

 bors, for the functional nuclei are so numerous as to make it improb- 

 able that they have all penetrated the thick membrana propria from 

 without. 



Cases have been encountered where this cutting off from the ovary 

 has already taken place when the ovum that left the corpus luteum is 

 in the two or four cell stage. On the other hand, the same condition 

 has been found when the youngest embryo in the incubatory pouch 

 contained about sixteen cells. From this time on, the remnant of the 

 corpus luteum becomes smaller and smaller, still remaining a compact 

 mass; but finally, when the ovum has divided into about sixty cells, 

 it disintegrates and disappears. 



6. Observations on Styela montereyensis. 



In this species the development of the follicular membranes pro- 

 gresses in much the same way as in Distaplia, but it is more difficult 

 to follow. The presence of a separate outer follicular epithelium, 

 however, is easily seen at a comparatively early stage; but, as is usual 

 with the simple ascidians, this epithelium is much thinner than the 

 inner follicle. 



The most interesting events in the life of the follicle of this species 

 are the degenerative changes which take place in the test cells, and 

 those of the inner follicular epithelium. In the latter the process is 

 comparatively simple, and consists only in the development of a large 

 refractive body in the cytoplasm of the cell. It is first seen at a stage 

 when the yolk is fully formed, and the maximum size of the ovum is 

 nearly reached, and appears as a small speck in the cytoplasm, so close 

 to the nucleus that it may have been extruded from the latter. It 

 rapidly increases in size, until, just before the egg leaves the ovary, 

 it is nearly as large as the nucleus of the cell and is surrounded by a 

 lighter area, which may, however, be due to shrinkage. Together 

 with this area it is about tlie size of the nucleus, which now occupies 

 an excentric position. It does not take nuclear stains well, but when 

 a safranin, gentian violet, and orange triple stain is used, it is colored 

 an opaque brown, that makes it the most conspicuous object in the 

 ovary. This body can have no reference to any future function of the 



