300 OBSERVATIONS ON WORMS. 



tion and multiplication, when divided into the small- 

 est pieces. Mliller, indeed, has noticed this pro- 

 perty which it possesses ; and states it moreover to 

 be the species which was the subject of Bonnet's 

 experiments, which are well known.* But what has 

 most struck me, is the readiness with which a severed 

 portion will acquire a fresh growth of parts, both 

 anteriorly and posteriorly, not merely when placed 

 in the same ditch-water in which it ordinarily lives, 

 and which may be conceived replete with animal and 

 vegetable matter, but when kept in pure pump- 

 water, renewed every day. Such water, when quite 

 fresh, rarely, if ever, is found to contain the smallest 

 animalculae, still less anything of a vegetable nature ; 

 so that one wonders whence the worm, under such 

 circumstances, can derive nutriment sufficient, not 

 merely for maintaining life, but for enabling it to 

 reproduce lost parts. How great must be its powers 

 of assimilation to elaborate a new head and tail from 

 the purest water in the course of a few days ! The 

 smallest portion, cut out of the middle of a perfect 

 worm, is not long in doubling its own length in each 

 direction. With the view of ascertaining what the 

 limits of its powers were in this respect, I, on one 

 occasion, put such a portion into distilled water, but 

 found that when thus treated it speedily died, with- 

 out acquiring any fresh growth. 



This little worm is at all times of so delicate a 

 structure, that, after being removed from its native 



* Experiences sur la reproduction d'une espece de .Vers d'eau 

 douce, CEuvres, torn. vi. p. 20. (8vo edit. Neuchatel, 1789.) 



