80 



HYDEOZOA. 



which its paralysing effects are to be attributed. The presence of these 

 remarkable organs is, however, by no means restricted to the tentacula ; 

 on the contrary, they are dispersed over various parts of the body, and 

 exist even in the folds of the ovarian membrane. In the latter situa- 

 tion, indeed, they are frequently extremely numerous, and compara- 

 tively of large size. 



CHAPTER V. 

 HYDEOZOA. 



(177.) THE HYD:ELS;, or freshwater polyps, are common in the ponds 

 and clear waters of our own country ; they are generally found creeping 

 upon confervse or submerged twigs, and may readily be procured in 

 summer for the purpose of investigating the remarkable circumstances 

 connected with their history. 



(178.) The body of one of Kg 3a 



these simple animals consists of 

 a delicate gelatinous tube, con- 6 



tracted at one extremity, which 

 is terminated by a minute suck- 

 er, and furnished at the oppo- 

 site end with a variable number 

 of delicate contractile filaments, 

 placed around the opening that 

 represents the mouth. 



(179.) When the Hydra is 

 watching for prey, it remains 

 expanded (fig. 39, 1, 2, 5), its 

 tentacula widely spread and 

 perfectly motionless, waiting 

 patiently till some of the count- 

 less beings that populate the 

 stagnant waters it frequents 

 are brought by accident in con- 

 tact with it : no sooner does an 

 animal touch one of the fila- 

 ments than its course is arrested as if by magic ; it appears instantly 

 fixed to the almost invisible thread, and in spite of its utmost efforts is 

 unable to escape ; the tentacle then slowly contracts, and others are 

 brought in contact with the struggling prey, which, thus seized, is gra- 

 dually dragged towards the orifice of the mouth, that opens to receive 

 it, and slowly forced into the interior of the stomach. 



