126 PLANARIA GRAMINEA. 



it bursts to allow an exit to its young ; and 

 the investing integument, scattered in the 

 surrounding element, disappears. Such is 

 the unalterable condition of its own exist- 

 ence. But this is only a single race. 

 The offspring, now independent, swim 

 through their native fluid, each revolving 

 on its centre as an axis, the whole under- 

 go the same gradations, and each is desti- 

 ned to be extirpated by the same fate 

 which destroyed its parent. 



By the death and subsequent decay of 

 the planaria graminea, eighteen eggs esca- 

 ped from its body. I do not affirm, how- 

 ever, that, like the volvox, the life of its 

 offspring is decreed to result from its own 

 destruction ; for circumstances have pre- 

 vented researches which might corroborate 

 the fact. No visible cause of death, in- 

 deed, was shown : Yet if life in the larger 

 animals hangs by so slender and delicate a 

 thread, that its perpetual rupture insensi- 

 bly ensues, even when danger is anxiously 

 warded away, how infinitely greater is the 



