SYNDICTYON RETICULATUM. 179 



in rows parallel to the circular tube, upon which are scattered large 

 lasso-cells. The actinal and polar axes are of about the same length ; 

 the veil is well developed (Fig. 295) ; the central part of the sphero- 

 some is uniformly arched outside ; the curve of the inner cavity is 

 concentric with it ; the proboscis extends somewhat Fig . 236- 



more than half the length of the height of the cav- 

 ity of the bell ; the circular and chymiferous tubes 

 are narrow (Fig. 296), of uniform diameter through- 

 out ; the sensitive bulb is ovoid, with a well-defined 

 lenticular-shaped concentration of black pigment- 

 cells (Fig. 293) ; the bulb itself is colored light- 

 brown ; the walls of the tentacles are thick, the 

 tentacular tube tapering rapidly as it nears the ex- 

 tremity of the tentacle, where the walls increase in 

 thickness in proportion as the tube diminishes in bore ; the bunches 

 of lasso-cells begin at some distance from the base of the tentacle (one 

 fourth of the length of the tentacle), increase rapidly in size, being 

 packed closer and closer towards the extremity of the tentacle, where 

 they are large crescent-shaped masses, almost touching each other, and 

 composed of very elongated lasso-cells. (See Fig. 292.) The tentacles 

 are not very contractile ; usually they are about as long as the vertical 

 diameter of the bell, and I have seen them contracted to about half 

 that length ; the peduncle is not contractile. The large lasso-cells of 

 the surface of the spherosome (Fig. 297) are round ; they are usually 

 scattered singly over the whole surface, while the fine granulation of 

 the surface of the bell consists of long, narrow cells, 

 dividing into smaller granules, which are small, un- 

 developed lasso-cells, forming a net-work over the 

 surface of the spherosome ; the lasso-cells are not 

 as numerous near the abactinal pole as towards 

 the margin of the bell, above the circular tube. 

 The motions of the Medusa are similar to those 

 of Sarsia, the bell, owing to its thinness, being, 

 however, much more flexible. The bell has a 

 very light metallic-blue tinge. The Hydroid was found growing on 

 Diphasia rosacea. Young Medusa?, similar to those developed from 

 the Hydroid, are found swimming freely about during June and 

 July. 



The young Medusa described above gradually loses the characters 

 which distinguished it from Sarsia, and as it becomes more advanced, 

 it resembles so closely Sarsia, that were it not for the invariable 



Fig. 29G. Fit;. 291, from the abactinal pole. 



Fig. 297. Part of net-work of the surface of the spherosome. c, large lasso-cells; c', cluster 

 of smaller ones. 



