300 FRESH-WATEE AQUABIA. 



offspring by germination, a small lump or tubercle will be 

 seen upon some portion of its body, and this gradually grows 

 and lengthens out until the small tentacles of the young 

 Hydra appear, which it begins to use for obtaining food 

 almost immediately. The young sometimes remain attached 

 to their parent's body until they are quite full grown, and 

 occasionally, indeed, until they themselves have also produced 

 children by germination. It not infrequently happens that 

 mother and datighter, though still closely united by family 

 ties, will both begin to devour the same unhappy worm, and 

 in a little time the relatives meet face to face near the 

 middle of their victim's body, which, however, generally 

 breaking in half, frees the captors from an awkward dilemma. 

 It does happen, though rarely, when two Hydras have attacked 

 the same worm, that the worm is too tough to be broken, 

 and the stronger polype swallows the weaker one and its prey 

 untU the prey has been digested, and then the vanquished 

 Hydra is rejected, or returned to its watery world to fish 

 and fight again, and none the worse, apparently, for its 

 rather tmpleasant experience. Polypes increase very rapidly 

 during the summer time by budding. 



Other lumps grow upon the body of Hydra besides those 

 which are to bud into young polypes, and these are called 

 sperm-cells or ovisacs. Both sperm-cells and ovisacs appear 

 upon the same Hydra. When the former are ripe, they burst 

 and discharge that which they contain, and thus fertUise the 

 ovum. After a time the ovum is extruded, and sinks to the 

 bottom of the water, where it remains for a long or short time, 

 according to the season, until it is hatched. The parent Hydra 

 dies after producing her egg. It very rarely happens that a 

 polype discharges more than one egg. The ova are about -^th 

 of an inch in diameter. The young Hydra, when first hatched, 

 possesses only two tentacles, which gradually increase in number. 

 Mr. James Fullagar, who has written in Science Gossip from 

 time to time some very interesting articles upon these creatures, 

 says that the young Hydrse have the power of stinging their 

 natural prey to death before they are old enough to devour it. 

 Hydrae which have been kept in captivity during the summer 



