ACALEPHiE. 
205 
eae h with a sort of fillet. These threads, which are oi extreme tena- 
<%, are thrown out when the animal is irritated by contact with any 
Grange body. We may see these filaments wrapping themselves round 
^eir prey, sometimes even penetrating its substance, and effectually 
^hduing the enemy. The green Hydra has thus a very simple 
Or ganisation. Nevertheless, it would he a mistake to say the animal 
^ '§• 87. Hydra viridis (Trembley). 1. Hydra magnified, bearing an embryo ready to detach 
itself. 2 . Animal, natural size. 3. Bud much magnified. 4. Bud, natural size. 
aia} ^Perfect, for it possesses everything necessary for its nourishment 
^°r the propagation of its species. 
here are learned men who have composed hundreds of volumes, who 
a J e Published whole libraries— naturalists and physicists who have 
fo 1 more than Voltaire ever penned, but whose names are utterly 
t^ttem On the other hand, there are some who have left only 
or three monograms, and yet their names will live for ever. Of 
174 , nnmber is the Genevois, A. Trembley. This writer published in 
1 1 a “Memoir on the Fresh-water Polypes.” In this little work he 
