HYDRA TUBA HABITS AND MODE OF CATCHING PREY. 71 



filament contracts and coils around the scarcely- 

 struggling wretch, -arm after arm involves it in 

 repeated folds, and slowly it is dragged towards the 

 Hydra's mouth, which gladly opens to receive the 

 prey. The trout that takes the mimic fly is not 

 more firmly held by the tenacious line, the landing- 

 net gapes not more widely for the captive fish, 

 until at length the fatal gate is passed, and the 

 swallowed victim finds itself plunged in the insatiable 

 stomach of its destroyer, where it is ultimately di- 

 gested and dissolved. 



Such is the voracity of the Plydra tuba, that its 

 real shape is only to be witnessed while the creature 

 is labouring under temporary abstinence from food; 

 for such is the capacity of its stomach, and so com- 

 pletely will the creature gorge itself, that it assumes 

 sometimes the appearance of a round ball, and indeed, 

 from excessive distension, will sometimes drop from 

 its point of adhesion and fall to the bottom of the 

 vessel. Neither is it at all nice in the selection of its 

 food ; it preys readily and greedily on most animal 

 substances, and the quantities it devours seem alto- 

 gether disproportioned to its dimensions. 



When sated, the Hydra remains motionless, with 

 the tentacula closely contracted. Judging by the 

 long-continued appearance of coloured food through 

 the skin, digestion is probably slow. The senses, if 

 such exist, excepting that of touch, are certainly 

 most obtuse. Hunger merely induces the extension 

 of the tentacula, but there is no evidence that the 

 presence of prey is discovered otherwise than by 

 actual contact. No searching activity of the tentacula 



