Notes on Medusa of the Western Atlantic. 143 



tocysts, and terminated by a suctorial cushion of the type common to many 

 of the Hydrozoa, having both muscular and glandular cells. At rest, the 

 end is cupped slightly. 



The arrangement of tentacle processes is not uniform in the several ten- 

 tacles of any individual. Sometimes no two tentacles exhibit just the same 

 plan in number and position of the t\vo different kinds of appendages. In 

 the case of the branches of the filamentous terminal process, they are seen to 

 follow a generally alternate plan. This is only roughly followed, however. 

 It is more noticeable in the first lateral processes that appear in the immature 

 medusa than it is later in life. In some instances two or three processes 

 grow out of the filament just at its junction with the main part of the 

 tentacle, but ordinarily a little space intervenes. There are from three to 

 eight of these branches on the average mature tentacle. In floating down- 

 ward in the water, the slender branches reach out far enough to cover an 

 area about three times the diameter of the bell, and as has been mentioned, 

 a considerably wider field is covered when the jelly-fish is resting on the 

 bottom. In this latter attitude, the filaments are held in such a position 

 that they just clear the bottom. They are strung with minute clusters of 

 nematocysts, with a slightly larger bead-like cluster at the end of each 

 branch. The whole system forms a very beautiful and at the same time 

 very efficient apparatus. Any luckless worm or copepod that happens to 

 touch this spider-web is instantly treated to a vigorous nettling by the dis- 

 charge of numbers of the nematocysts. Although these are small in size, 

 they do their work in thoroughly efficacious fashion, the victim succumbing 

 with hardly a struggle. 



Feeding reactions. After the discharge of the nettling cells there is no 

 trouble in getting the prey to the mouth. The slender snares are instantly 

 retracted, the entire tentacle shortens and curves towards the mouth, the 

 bell-muscles contract spasmodically, the manubrium is set in eager motion, 

 and the whole organism evinces the keenest interest in the prospect of a 

 meal. Upon coming into contact with the spherical masses of stinging cells 

 at the end of the manubrium, around the mouth, still further punishment is 

 dealt out to the victim. 



When one realizes that the warm waters of the moat are even more 

 richly supplied with small creatures than the ordinarily teeming tropical seas 

 in the neighborhood of coral shoals, it is easy to see that so well-equipped 

 a fisherman as this should have no trouble in making a living. It is no 

 wonder, then, that this species has become well established. Although the 

 first individuals may have come into the locality within comparatively recent 

 times, as we may conclude from the retention of the open-sea characters 

 already mentioned, the genus being evidently a readily mutable one, such 

 favorable conditions as have been described for the species might easily ex- 

 plain the presence of such very great numbers as were observed in the moat. 



