52 THE MICROSCOPE. 



appears on the hydra's body; this grows larger, and 

 divides at its apex into several minute papillae, which 

 afterwards become the tentacles. When reproducing 

 by ova, the observer will notice certain peculiar eleva- 

 tions on the body of the hydra, some, in the middle 

 of the body, round; others, at the bases of the 

 tentacles, of a conical shape; perhaps one or two ot 

 each kind. The round elevations contain the ova; 

 the conical, the spermatozoan bodies. The ovum, 

 when ripe, pushed through the body-wall, and impreg- 

 nated, becomes attached to some water-weed, and 

 awaits the warm spring to be developed into the young 

 hydra. But I have never succeeded in meeting with 

 these detached ova, and they appear to have been 

 only noticed by few. Trembley and Baker record 

 many and various experiments practised by them on 

 the hydra; and the former gives us a number of 

 admirably executed figures. The result of these ex- 

 periments may be summed up in the language of 

 Dr. G. Johnston: "If the body is halved in any 

 direction, each half in a short time grows up a perfect 

 hydra ; if it is cut into four or eight, or even minced 

 into forty pieces, each continues alive and developes 

 a new animal, which is itself capable of being mul- 

 tiplied in the same extraordinary manner. If the 

 section is made lengthways, so as to divide the body 

 into two or more slips, connected merely by the tail, 

 they are speedily re-soldered, like some heroes of fairy- 

 tale, into one perfect whole ; or if the pieces are kept 

 asunder, each will become a polype, and thus we may 

 have two or several polypes with only one tail between 

 them ; but if the sections be made in the contrary 

 direction from the tail towards the tentacula you 

 produce a monster with two or more bodies and one 

 head. If the tentacula the organs by which they 

 take their prey, and on which* their existence might 



