MUSEUM OF COMPARATIVE ZOOLOGY. 109 



the polypide and towards the margin is the funiculus, fun. Between it 

 and the neck of the polypide the ccelomic epithelium is thickened and its 

 cell boundaries have become evident. Directly above this region, and im- 

 mediately above the muscularis, is a row of cells, which stain deeply and 

 show other evidences of being embryonic. These are directly continuous 

 with the neck cells of the older polypide, exactly as was the case with 

 the cells of the inner layer in Figures 4 and 6 (Plate I.). In fact, they are 

 in every way comparable with these. Figures 8 and 9 (Plate II.) show 

 slightly later stages. The funiculus has moved farther from the parent 

 bud, the future outer layer (ex.) has become thicker, and its cells are 

 columnar and sharply marked off from each other. The inner layer (i.) 

 of the new individual is represented by a thicker, stolon-like mass of cells, 

 which is in direct continuation with the inner layer of the mother bud, 

 from which it was doubtless derived. 



A stage which, on account of the greater distance of the funiculus 

 from the older polypide, I believe to be slightly more advanced than 

 Figure 8, is shown in Figure 9. In the section drawn, the inner cell 

 mass (i.) exhibits few nuclei, but they are more numerous in adjacent 

 sections. The band of protoplasm connecting this young bud with the 

 mother is perceptibly smaller than in the preceding stage. The cells of 

 the inner layer form a mass sharply marked off from the ectoderm ; 

 those of the outer layer are greatly thickened, as in the last stage. 



A peculiar thickening of what I regard as Nitsche's " Stutzlamella " 

 takes place between the young bud and the mother polypide. This is 

 shown in Figures 9 and 10 at mu. It is not stained by Czoker's cochi- 

 neal, and the circular muscle fibres, here cut transversely, are very con- 

 spicuous in the midst of it. As I have noticed this appearance only in 

 the cases of young buds which have originated like those of Figures 9 and 

 10, and of others of about their age, (and it is in these buds and at this 

 age that migration from the older polypides takes place,) I believe that 

 there is some connection between this condition of the muscularis and 

 the disturbance which such a migration must cause. 



I have already (page 106) referred to the fact that in some cases me- 

 dian buds are found far removed from the mother polypide, although 

 in an early stage of development. Stage IV. is the youngest in which 

 such buds have been found. 



The cells of the mass destined to form the inner layer of the bud 

 multiply rapidly after they have reached a proper position, and there is 

 considerable protrusion of the coelomic epithelium into the body cavity. 

 The fact, that during its extensive migration the bud increased only 



