I 



FolUch-cells in Salpa. 95 



liEematoxylin, borax-carmine, or saffranln. Outside the 

 blastomere is a mass of more coarsely Granular and deeply 

 staining protoplasm, in which no cell-walls can be discovered, 

 bnt in which appear many nuclei, all exactly resembling the 

 nuclei of the follicular epithelium. These have a definite 

 chromatic reticulum with rather small nodal swellings and no 

 nucleolus. 



Within the protoplasm of the blastomere as shown in this 

 one section are seven bodies similar in size to the follicle 

 nuclei just described, but quite different in appearance. [ 

 believe them to be ingested follicle nuclei. They do not 

 stain so deeply as the nuclei outside, though they are much 

 darker than the protoplasm of the blastomeres in which they 

 lie. We do not find in them the clear cut chromatin reticu- 

 lum with sharp contours, such as we see in the follicle nuclei, 

 but in certain of them we do find what appears to be such a 

 chromatic reticulum degenerating because undergoing diges- 

 tion. Observe especially the nucleus a. The reticulum is 

 evident, and I think no one can doubt that the body is really 

 a nucleus. Compared with the follicular nuclei the reticulum 

 is seen to stain less deeply and the fibrils and nodal masses 

 do not have sharp contours. The whole appearance indicates 

 the beginning of disintegration. I believe this nucleus to 

 have been ingested but a short time previous to the killing of 

 the embryo. At h and c are nuclei which have gone further 

 in the process of degeneration, the chromatin threads being 

 more diffuse. At d, e, /, and g we see a further stage in the 

 same process, and at A, j, and k we observe within the 

 ingested nuclei an almost evenly granular mass of disinte- 

 grating chromosomes. In other blastomeres and in another 

 section of this same blastomere one can observe the last step 

 in the degeneration, a mere mass of debris no longer delimited 

 by a nuclear membrane from the surrounding protoplasm of 

 lhe blastomere. 



Notice that the less degenerated of these ingested nuclei 

 lie on the side nearer the periphery of the embryo. The 

 inwandering follicle-cells, as they push toward the centre of 

 the embryo, penetrate the blastomeres that lie in their path. 

 Apparently the most recently ingested nuclei, entering from 

 the peripheral side, crowd the partly digested ones toward 

 the inner side of the blastomere, giving the appearance figured. 

 Not every section of a blastomere shoCv'S such diagrammatic 

 arrangement, but this condition is noticeably frequent. The 

 section figured was chosen because of the diagrammatic way 

 in which it shows this point and because of the clearly nuclear 

 nature of the body a. 



