PLATE V 



Fig. 1. Half of the keel of a VeleUa measuring one and a half inches in length, shomng the principal 

 tube V, with its anastomoses extending to the broad marginal canal, from which proceed the 

 dendritic tubes extending to the edge of the mantle of the keel of Figs. 4, 5. 



Fig. 2. Somewhat more magnified view of a portion of the keel of the preceding figure, sho'srag more 

 distinctly the principal central branch, with its anastomoses, and the large blind sac-like 

 pouches (see Fig. 10) formed along certain parts of the main circular canal of the keel. The 

 pouches are filled with clusters of yellow cells; there are also smaller patches of yellow cells 

 in the circular canal. 



Fig. 3. Still more magnified than preceding figure, to show the position of the clusters of yellow cells y, 

 near the edge and in the circular canal. 



Fig. 4. Half of the keel of a VeleUa slightly larger than the preceding figures, showing the main central 

 vascular branch i; the amastomosiiig branches v", extending over the whole surface of thu 

 keel to the circular canal v", running nearly parallel to the outer free edge of the keel. From 

 this circular canal branch off the dendritic canals v', which unite again along the free edge 

 of the mantle of the keel. 



Fig. o. Magnified view of two of the dendritic canals of the free edge of the mantle of the keel ; 

 v°, circular canal, from which arise the main branches v', of the dendritic canals v", which 

 unite again in a marginal canal v"', along the outer edge of the keel mantle. 



Figs. 6, 9. Ramifications of the vascular system from the lower side of the float, with clusters of appar- 

 ently decomposed or dead yellow cells. 



Fig. 7. Magnified view of the frill-Uke ramifications, v v', of the so-called dendritic branches of the 

 vascular system of Fig. 5, with small clusters of yellow cells c c'. 



Fig. 8. Enlarged view of tubes of the vascular system of the keel, to show the mode of ramification and 

 anastomosis over the surface of the keel. 



Fig. 10. (See Fig. 2.) 



Fig. 11. General appearance of the net- work and principal branches of the so-called liver system IV, 

 under the conical part of the float a ; seen in profile. 



Fig. 12. General view of the ramifications of the same system, extending under the float; seen from above. 



Fig. 13. Branch of liver system and anastomoses at the junction of the float and of the horizontal mantle. 



