570 MAYNARD M. METCALF, 



cells, as they push toward the center of the embryo, penetrate the 

 blastomeres that lie in their path. Apparently the most recently in- 

 gested nuclei, entering from the peripheral side, crowd the partly 

 digested ones toward the inner side of the blastomere, giving the ap- 

 pearance figured. Not every section of a blastomere shows 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. 



As before mentioned, Brooks has given exactly this interpretation 

 of the bodies within the blastomeres and this confirmatory note would 

 be uncalled for except for Heider's and Korotneff's more recent 

 papers giving a different interpretation. It is possible that in S. run- 

 cmata-fusiformis (the species Heider studied) not only the follicle 

 nuclei, but also their cytoplasm may be ingested by the blastomeres, 

 but I am more inclined to believe Heider was mistaken when he 

 figured these bodies as nucleated cells. His figures are not drawn 

 with careful attention to detail, so it is hard to judge from them. 

 In S. pinnata and S. hexagona no cell walls can be made out in the 

 mass of migrated follicle cells. It is therefore by no means probable 

 that the cytoplasm of the follicle cells could be seen if it were in- 

 gested with the nuclei. This is especially true in view of the digestive 

 action upon these bodies within the blastomeres. 



Korotneff's and Salensky's statements that these bodies con- 

 tain no trace of a nucleus within them is, of course, true if they be 

 themselves nuclei. 



In the young ovarian eggs of the rat I have found indisputable 

 evidence of a similar ingestion of follicle cells. In the figure drawn 

 (Fig. 62, Plate 38) is shown a single ovum with its whole follicle. 

 The nucleus of the ovum is large and presents the usual appearance. 

 The outer contour of the egg is distinct giving a clear cut boundary 

 between the protoplasm within and the follicle. The follicle cells 

 show no cell walls, their many nuclei seeming to lie in a common 

 mass of protoplasm. The follicle nuclei show clearly a fine chromatic 

 reticulum with many nodal swellings, one or more of which may be 

 so large as to resemble nucleolei. A few of the cells in the outer 

 layer of the follicle have dark nuclei due to the closeness of the 

 reticulum. 



Inside the ovum itself we see, in this section, three, perhaps four, 



