SEA-FAN MAKERS. 



181 



in a transparent vesicular membrane, dotted with 

 many minute calcareous grains, and marked with 

 eight white longitudinal lines or septa, which, stretch- 

 ing between the membrane and the central stomach, 

 divide the intermediate space into an equal num. 

 ber of compartments. These lines not only extend to 

 the base of the tentacles, 

 but run across the disk, 

 and terminate in the cen- 

 tral mouth. The tentacles 

 are short, obtuse, fringed 

 on the margins, and 

 strengthened at their base 

 by numerous linear straight 

 crystalline spicules. From 

 the base of the white 

 longitudinal lines an equal 

 number of white tortuous 

 glandular filaments de- 

 pend, hanging loose in 

 an abdominal cavity placed underneath the fleshy 

 cylindrical stomach, and continuous with the canals. 

 The polyp-cells are oval, placed just beneath the 

 skin, and are the terminations of the long water- 

 bearing canals which run through the whole polype- 

 mass. These canals divide, as they proceed, into 

 branches, which diverge towards the circumference, 

 and there expand into cells ; they have strong, per- 



FIG. 33. " COW'S PAP " 

 (Alcyonium digitatuni) . 



