HYDROIDA. 199 



This fact is the more remarkable, when it is contrasted with the 

 fate which awaits the worms oq which they feed. No sooner are these 

 laid hold upon than they evince every symptom of painful suffering ; 

 but their violent contortions are momentary, and a certain death sud- 

 denly follows their capture. How this effect is produced, is mere 

 matter of conjecture. Worms, in ordinary circumstances, are most 

 tenacious of life, even under severe wounds ; and hence one is inclined 

 to suppose that there must be something eminently poisonous in the 

 Hydra's grasp; as it is impossible to believe, with Baker, that this 

 soft toothless creature can bite and inject a venom into the wound it 

 gives. " I have sometimes," says Baker, " forced a worm from a polyp 

 the instant it has been bitten (at the expense of breaking off the polyp's 

 arms), and have always observed it to die very soon afterwards, with- 

 out one single instance of recovery." Trembley states as a fact, that 

 fishes cannot be made to swallow hydrse, seeming to prove the presence 

 of some irritating quality in the latter. 



The body of the Hydra virvdis is said by Ecker to be composed of 

 a vital contractile substance, soft, granular, and elastic, which is reti- 

 culated with clear spaces, containing more or less clear fluid. This 

 contractile substance, from its want of definite form, cannot, according 

 to Ecker, be termed muscular. " It is distributed throughout the whole 

 body, and not formed into filaments or fasciculi j nor any more is the 

 sensitive substance yet collected into nerves, but must be assumed to 

 be dispersed through the whole body. The one is always most inti- 

 mately connected with the other, as the investigation of all the lower 

 animal forms teaches us. It is not until nerves are developed, that 

 even scattered muscles are assigned for any given purpose in the 

 economy. Muscles are not possible without a connecting nervous 

 system." 



The tentacles, or feelers, are tubular, and filled with an albuminous 

 fluid. They are furnished with a variable number of tubercles, arranged 

 in a spiral manner on the surface. These tubercles are beset with a 

 number of spinigerous vesicles,, which serve as organs of touch, in the 

 midst of which, at the apex of the tubercle, a very singular organ of 

 prehension is situated. Each spinigerous vesicle consists of two sacs, 

 placed one within the other, with a small cavity in the centre of the 

 inner one. At the point of contact of the two sacs is placed a long 

 ciliary hair, which projects from the surface of the tentacle. The organ 

 of prehension, which is called the hasta, consists of a sac opening at 

 the surface of the tentacle, within which, at the lower portion, is placed a 

 saucer-shaped vesicle, supporting a minute ovate body, which agaia 



