380 SYDNEY J. HIOKSON. 



buds. The epithelium of the central portion of these filaments 

 is precisely the same as that of the stomodasum, the cells being 

 smaller^ and staining more deeply in borax carmine than the 

 endoderm-cells, so that there can be little doubt that "Wilson 

 (38) is correct in saying that (in Funiculina) the dorsal 

 mesenterial filaments are of ectodermic origin. 



The tentacles do not appear until quite late in the develop- 

 ment of the bud^ — not^in fact, until after the formation of the 

 ventral mesenterial filaments, which arise as thickenings of the 

 endoderm at the edge of the mesenteries. 



Section V. — Note on the Circulation of the Fluids in 



THE Polyps. 



In a communication I made to the Royal Society in 1882, 1 

 pointed out that the action of the cilia in the siphonoglyphe of 

 Alcyonium was to create a current of water flowing from the 

 mouth into the ccelenteron. Almost simultaneously, Wilson 

 discovered that the cilia of the dorsal mesenterial filaments 

 produce a current flowing in the opposite direction. 



During the month of December I examined these currents 

 again with great care, and I can now confirm not only my own 

 results, but also those of Wilson. 



When the polyps of Alcyonium digitatum are fully 

 expanded, the long cilia of the siphonoglyphe are in active 

 movement, causing a swift current of water to flow into the 

 ccelenteron on to the six endodermic — that is to say, ventral — 

 mesenteries. A reverse current from below upwards towards 

 the mouth is produced by the cilia of the two long dorsal or 

 ectodermic mesenterial filaments. 



The current produced is a tolerably swift one, and must 

 cause a rapid distribution of any soluble products of the diges- 

 tion caused by secretion of the gland-cells of the mesenterial 

 filaments, and there can consequently be little doubt that the 

 filaments are not alone the absorbents of the food materials in 

 solution. These must be carried down by the ciliary currents 

 to the lower parts of the coclenteric tube, and absorbed by the 

 endoderm in any region of the tube. 



