PLATE. V 
Fic. 1. Half of the keel of a Velella measuring one and a half inches in length, showing 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. 
Somewhat more magnified view of a portion of the keel of the preceding figure, showing more 
distinetly the principal central branch, with its anastomoses, and the large blind sac-like 
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pouches (see Fig. 10) formed along certain parts of the main circular canal of the keels The 
pouches are filled with clusters of yellow cells; there are also smaller patches of yellow cells 
in the circular canal. 
Fic. 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. 
Fie. 4. Half of the keel of a Velella slightly larger than the preceding figures, showing the main central 
vascular branch v, the amastomosing branches v’, extending over the whole surface of the 
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. 
Fic. 5. 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. 
Magnified view of the frill-like ramifications, vv, of the so-called dendritic branches of the 
vascular system of Fig. 5, with small clusters of yellow cells cc’. 
Fig. 8. Enlarged view of tubes of the vascular system of the keel, to show the mode of ramification and 
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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 JV’, 
under the conical part of the float a; seen in profile. 
Fic. 12. General view of the ramifications of the same system; extending under the float; seen from above. 
Fic. 13. Branch of liver system and anastomoses at the junction of the float and of the horizontal mantle. 
