216 



disintegrating chromosomes. In other blastomeres and in another sec- 

 tion of this same blastomere one can observe the last step in the dege- 

 neration , a mere mass of debris no longer delimited by a nuclear 

 membrane from the surrounding protoplasm of the 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 center 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 appea- 

 rance figured. Not every section of a blastomere shows such diagram- 

 matic 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 

 uf the bodies within the blastomeres and this confirmatory note would 

 . be uncalled for except for H e i d e r 's and Korotneff's more recent 

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

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

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

 but I am more inclined to believe H e i d e r 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. pin- 

 nata and *S'. hexagona no cell walls can be made out in the mass of mi- 

 grated follicle cells. It is therefore by no means probable that the cyto- 

 plasm of the follicle cells could be seen if it were ingested 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. 



References to Literature: 



Ï o d a r o , Sui primi fenomeni dello sviluppo delle Salpe: Atti Reale Accad 

 Lincei, Trans. Voi. 4. p. 86. 



— II. Sur les premiers phénomènes du développement des Salpes: Arch. Ital. 

 deBiol. Vol. 2. p. 1. 



Salensky, Neue Untersuchungen über die embryonale Entwicklung der 

 Salpen: Mittheil. a. d. Zool. Stat. zu Neapel. 4. Bd. p. 90—171 and 327—402. 



Brooks, The Genus Salpa: Memoirs from the Biological Laboratory of the 

 Johns Hopkins Univ. Vol. II. p. 1—303. 



Heider, Beiträge zur Embryologie von Salpa fusiformis Cuv.: Abhandl. d. 

 Senckenb. naturf. Ges. Bd. XVIII. p. 367—455. 



