﻿April, 1857.] 



ELLIOTT SOCIETY. 



183 



In view of their idiosyncracy, their appearance at an early pe- * 

 riod of existence, and their almost universal presence among Ex- 

 ostomata, their entire absence even in the earliest stages of 

 growth among Endostomata, introduces a marked distinction be 

 tween the two sub-orders. 



1st. group. CAMPANULARIDJE. 



The Medusas belonging to this group are usually cymbaloid or 

 disk-like in form; more rarely they are campanulate ; sometimes 

 umbrellashapejd. The disk is of very various thickness and solidity, 

 and its external surface apparently always perfectly smooth, and 

 homogeneous. The digestive cavity is always a short cylindrical 

 organ usually cleft into four petaloid labial tentacuia around the 

 mouth. It is sometimes sessile, sometimes pedunculate. The 

 radiate tubes vary in number but usually they are limited to four. 

 In their course are the sexual glands, which sometimes occupy 

 but a very limited area, at points varying according to the genus; 

 sometimes stretch from the base of the digestive trunk to the mar- 

 ginal cube ; sometimes are connected at once with the wall of the 

 digestive cavity, and with the radiate tubes. The tentacuia are 

 always (?) more than four, sometimes extremely numerous. They 

 are usually provided with a prominent bulb at their point of attach- 

 ment. Besides the tentacuia there are nearly always present 

 small prominences, bearing tliread-cells, which I think are distinct 

 from the rudiments of tentacuia in course of development. All ot 

 these, besides the marginal capsules (present in the greater num- 

 ber of genera, comprising the group) are each connected with a 

 ganglion-like enlargement of the colored marginal cords, (PI. 12. 

 hg. 1-2, a, b, c,) which I regard as the principal portion of the nervous 

 system. There is a third class of tentacuia, very small transpa- 

 ent structures, belonging to a limited number of genera, which 

 have no immediate connection with the marginal cord, but appear 

 to be appendages of the outer cellular layer of the disk. These 

 are variously arranged being sometimes nearly connected with 

 the bases of the other tentacuia, sometimes isolated. The mar- 

 ginal capsules are usually round or oval in form, (in the latter 

 case attached by their longer side) and containing a variable 

 number of corpuscles, which do not contain inorganic deposit. (?) 

 They vary also in number, but the typical number appears to be 

 eight and these are placed two between every two radiate tubes, 

 so that one of the latter, always falls midway between two mar- 



