ACALEPH^E. 



203 



each with a sort of fillet. These threads, which are of extreme tena- 

 city, are thrown out when the animal is irritated by contact with any 

 strange body. We may see these filaments wrapping themselves round 

 their prey, sometimes even penetrating its substance, and effectually 

 subduing the enemy. The green Hydra has thus a very simple 

 organisation. Nevertheless, it would be a mistake to say the animal 



Fig. 87. Hydra viridris (TrembleyX 1. Hydra magnified, bearing an embryo ready to detach 

 itself. 2. Animal, natural size. 3. Bud much magnified. 4. Bud, natural size. 



was imperfect, for it possesses everything necessary for its nourishment 

 and for the propagation of its species. 



There are learned men who have composed hundreds of volumes, who 

 have published whale libraries naturalists and physicists who have 

 written more than Yoltaire ever penned, but whose names are utterly 

 forgotten. On the other hand, there are some who have left only 

 two or three monograms, and yet their names will live for ever. Of 

 this number is the Genevois, A. Trembley. This writer published in 

 1741 a " Memoir on the Fresh-water Polyps." In this little work he 



