102 TRANSACTIONS LIVERPOOL BIOLOGICAL .SOCIETY. 



condition the tentacles and bod}- wall of the anthocodise 

 are very transparent, and many features of the anatomy 

 can be seen without dissection.* 



The details of anatomy that can be seen in a living 

 anthocodia are as follows : — From the mouth there hangs 

 down into the body cavity a short opaque throat — the 

 stomodseum (St.) — which opens freely below. At this — 

 the lower — aperture six short sinuous cords, the mesen- 

 terial filaments, arise attached to the free edges of six 

 very thin vertical plates — the mesenteries (conf. PL I., 

 tig. 4, PL II., fig. 15, Mst.) — and, in addition, there are two 

 cords which pass straight down into the cavity of the 

 polyp attached to the free edges of the two remaining 

 mesenteries. These two straight cords are called the 

 dorsal mesenterial filaments, and the mesenteries which 

 support them the dorsal mesenteries. The other mesen- 

 teries are called the dorso-laterals, ventrolaterals and 

 ventrals respectively. 



Further details can only be studied in preparations 

 made for microscopic examination. 



Nematocysts. — The pinnules of the tentacles bear a 

 number of very minute stinging organs- — the nematocysts. 

 They are extremely small (0' 0075mm. in length), and may 

 be easily overlooked. They are oval in shape, and when 

 irritated discharge a plain unarmed thread (PL II., figs. 

 8, 9, 10 and 11). Each nematocyst is formed within a 

 specialised ectodermal cell called the " cnidoblast."' 



The Stomodjstjm is lined internally by a columnar 

 ciliated epithelium, usually thrown into a number of folds 

 in the preparation. On one side there is a groove lined 

 by specialised epithelium armed with relatively long 

 * The transparency varies in specimens from different localities. In 

 some cases there are so many spicules in the anthocodia that the trans- 

 parency is very considerably diminished, The figure 4 in Plate I. was 

 drawn from a Plymouth specimen. 



