Hydka. Z. HYDROIDA. 103 



momentary and a certain death suddenly folloivs their capture. How 

 this effect is produced is mere matter of conjecture. Worms, in or- 

 dinary circumstances, are most tenacious of life even \inder severe 

 wounds, and hence one is inclined to suppose that there must l)e 

 something- eminently poisonous in the Hydra's grasp, as it is impos- 

 sible 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 polype the instant it has been 

 bitten, (at the expence of breaking off the polype's arms,) and have 

 always observed it to die very soon afterwards, without one single 

 instance of recovery."* To the Entomostraca, however, its touch is 

 not equally fatal, for I have repeatedly seen Cyprides and Daphnise 

 entangled in the tentacula and arrested for some considerable time, 

 escape even from the very lips of the mouth, and swim about after- 

 wards unharmed ; perhaps their shell may protect them from the 

 poisonous excretion — The grosser parts of the food, after some hours' 

 digestion, are again ejected by the mouth ; but, as already mention- 

 ed, the stomach is furnished with what, in one sense, may be called 

 an intestine to which, according to Trembley and Baker, there is an 

 outlet in the centre of the base, and the latter asserts that he has, 

 " several times, seen the dung of the polype in little round pellets 

 discharged at this outlet or anus."f 



* Hist, of the Polype, 33 — comp. with 67-8 " That insigiiilicant and inac- 

 tive insect called the fresh water polypus, of all poisonous animals, seems to 

 possess the most powerful and active venom. Small water-worms, which the 

 polypus is only able to attack, are so tenacious of life, that they may be cut to 

 pieces without their seeming to receive any material injury, or to suffer much 

 pain from the incisions. But the poison of the polypus instantly extinguishes 

 every principle of life and motion. What is singular, the mouth or lips of the 

 polypus have no sooner touched this worm than it expires. No wound, how- 

 ever, is to be perceived in the dead animal. By experiments made \\\t\\ the 

 best microscopes, it has been found, that the polypus is neither provided with 

 teeth, nor any other instrument that could pierce the skin." Smellie's Phil, of 

 Nat. History, ii. 462 — The fact that fishes cannot be made to swallow Hydraj, 

 seems to prove the presence of some irritating quality in the latter See Trem- 

 bley, Mem. 137. 



f Lib. s. cit. 27. — He adds, — " Much the greater and grosser part of what 

 the polype eats, is most certaiidy thrown out again by the mouth, after lying a 

 proper time to become digested in the stomach -. and, for a good while, I ima- 

 gined there was no other evacuation ; but am now convinced, that the finer part, 

 in small quantity, is carried downwards through the tail, and passed off that way. 

 I believe however there is also another purpose to which this passage serves, 

 and that is, to convey a mucus or slimy matter to the end of the tail, for its 

 more ready adhesion to sticks, stalks, or other bodies." 



