Chap. I. ADULT MEDUSA OF CORYNE MIRABILIS. 213 



The main bulk of the body consists of a gelatinous mass, forming the bell- 

 sbajjed, central part of the animal. This is thickest above, in the central part 

 of the swollen disk (wood-cut 29, a b); towards the sides it gradually tapers, 

 and becomes very thin near the lower margin, about the origin of the tentacles, 

 where it is suddenly turned inward, at right angles with its previous direction, 

 and forms a transverse partition (wood-cut 31, c\ and PI. XVIII. Fig. 17, a), the 

 so-called veil, between the main cavity of the body and the surrounding medium, 

 a large hole, however, being left in the centre, through which the proboscis plays 

 at ease. 



At first, when watching the animal in its movements, it would seem as if the 

 gelatinous mass itself were the cause of locomotion ; but, upon close examination, 

 it is easily found that it is merely an elastic support for the active ajiparatus 

 of motion, Avhich consists of layers and bundles of contractile cells, diversely arranged. 

 There is an external system of these bundles, immediately under the epidermis, 

 through the agency of which the contracted body is restored to its expanded 

 form. Upon the inner surface there is another system, which contracts the sphere, 

 acting in antagonism with the former. These two systems consist of bundles 

 extending vertically from the upper portion of the vault downward. Within the 

 inner vertical system, there is another one consisting of concentric transverse bun- 

 dles, lining the cavity of the body, the direction of which tends to reduce the 

 capacity of the sjiace inclosed between the walls of the animal and the lower 

 partition. A fourth system of circular concentric bundles is spread through the 

 whole partition below. This last system, in its strongest contractions, may shut 

 almost entirely the main cavity of the body, and, like the pupil of the eye, it 

 opens and shuts constantly. In its less powerful contractions, it assists the inner 

 transverse and vertical muscles in reducing the capacity of the inner cavity, and 

 when deeply contracted, it helps, more fully than any other part of the contractile 

 system, in forming the body into a sphere. Thus -we have here four distinct 

 motory systems : an external superficial system, an inner system, parallel to the 

 former, a concentric system of the main cavity, and a concentric system of the 

 partition below. 



The nutritive system, with its ramifications, gives a peculiar aspect to this genus, 

 and contributes greatly to its remarkable appearance. From the mere impression 

 derived from the powerful movements and the great activity of the proboscis of 

 this animal, we are at once led to infer that it is very voracious, the proboscis- 

 like digestive cavity and the nettling appendages being well calculated to seize 

 upon a living prey. This system begins with a central proboscis, of considerable 

 size and length in proportion to the bulk of the body. It hangs down from the 

 middle of the vault, and assumes the most diversified forms, in its various con- 



