HYDRA. 



27 



which is coiled up a long and delicate filament, not unaptly com- 

 pared to the lasso used by Brazilian horsemen 



The neck of each vesicle is furnished with three sharp spines, 

 which, when the arms are prepared to seize the prey, become erect 

 and prominent. The mode of action of these weapons is as simple 

 as the result is efficacious. The " lasso-threads," with their viscid 

 extremities, speedily involve the seized victim in their tenacious 

 folds, and closely bind it against the spines with which the skin 

 of the hydra is studded ; these, probably, in their turn, become 

 prehensile instruments, and moreover apparently form an appa- 

 ratus of poison fangs of a very deadly character, for it is observable 

 that an animal once seized by the hydra, even should it escape 

 from its clutches, almost immediately perishes. 



We have dwelt at some length upon the history of the hydra, 

 partly on account of the interest which attaches to an animal so 

 simple in its apparen structure and yet so formidably armed, but 

 more especially because it is the type of a large class of beautiful 

 creatures, to which we must now beg the attention of the young 

 naturalist. 



The Hydrse, as we have 

 seen, are capable of loco- 

 motion, and wander about 

 from place to place ; but a 

 vast majority of the animals 

 most nearly allied to it in 

 organization, in their adult 

 condition are fixed to some 

 foreign object upon which 

 they grow. 



The Club Hydrae (Coryne)* 

 for example (Fig. 19), are always 

 found growing upon the surface 

 of some shell or stone, to which 

 they seem rooted by the extre- 

 mity of a horny tube in which 

 they live. In these creatures the 

 upper part of the body is dilated 

 into a kind of club-shaped head, 

 armed with tentacula, which, in- 

 stead of being arranged in a 

 single circle around the mouth, 

 are distributed irregularly over the exterior in such a manner that, at first sight, 



FIG. 19. CORYNE: a b, magnified; c, natural size. 



], korune, a club. 



