Notes on the morphology of the Tunicata. 571 



distinct nuclei beside the germinal vesicle, and also a bilobed group 

 of granules on the opposite side of the egg. The small nuclei within 

 the egg almost exactly resemble the nuclei of the follicle cells, except 

 that they do not stain so deeply with haematoxylin. The double 

 group of granules on the other side of the egg seems to be the rem- 

 nant of two ingested nuclei which have been nearly digested. In the 

 two lower of the four ingested nuclei on the other side we observe 

 that the finer threads of the chromatic reticulum are lost, little ex- 

 cept the nodal swellings remaining. The granules in the double group 

 opposite are of the same size as these nodal swelHngs of the chromatin 

 reticulum. I believe they should be so interpreted and be regarded 

 as the last remnant of two nuclei whose nuclear membrane and the 

 finer threads of whose chromatic reticulum have already been digested. 

 Of the nuclei figured as lying apparently within the contour of the ovum, 

 all but one are shown by careful focussing to be actually within the 

 ovum and on a level with the germinal vesicle. One, however, the 

 darker one, is at a little lower level and probably lies just outside 

 the egg membrane, and should therefore not be counted as one of 

 the ingested cells. 



The ovum drawn gives the best demonstration of the ingestion 

 of follicle nuclei that I have seen. In numerous ova of this size, 

 however, I have seen paranuclear bodies which are clearly follicle 

 nuclei. About half of the ova in this stage of their development 

 seemed to be devouring the nuclei of the follicle. In larger ova I 

 have not seen this process ^). 



1) I have as yet examined but a single ovary. I hope, however, 

 in the near future, to carry this investigation further and make a 

 comparative study of the ovarian eggs of different Mammals and other 

 Vertebrates, to see, if possible, if the conditions described are normal, 

 and, if so, how general these j^henomena are. The ingestion of follicle 

 cells by the ova of Vertebrata has been mentioned a number of times. 

 Balfour (in: Quart. Journ. micr. Sc, V. 18, p. 394), Mac Lead (in: 

 Arch. Biol., V. 1, tab. 8, figs. 7 and 9) and van Beneden (ibid., 

 V. 1, tab. 21, fig. 14) describe a syncytium of ovarian cells in the 

 shark and the bat and show that only one, or at most a few, of the 

 several cells in each syncytium persist as definitive ova, the others 

 serving as food for the survivors. The phenomena I have described 

 for the rat occur in much older ova with double follicle, but may per- 

 haps be regarded as an interesting variety of the same fundamental 

 process. 



