404 APPENDIX. NOTES. 



It seems not accordant with the usual accuracy of this 

 great Philosopher and Naturalist, where he is treating 

 formally of the same kind of object, to distinguish it by 

 two different names, nor is it likely that he would have 

 placed them in separate chapters, as if they were distinct 

 things. He would surely not have devoted one whole 

 chapter to the Tethys and Acalephe, and another to the 

 Cnide and Sponge, unless he had meant they should be 

 considered as distinct animals. Still there is one circum- 

 stance that seems in one respect to indicate their identity, 

 one species of each appears to be usually fixed, and the 

 other free. But this, by itself, does not furnish a satis- 

 factory proof. With regard to these Acalephes or Cnides 

 of Aristotle having any right to be considered as belonging 

 to Linne's genus Medusa, it seems chiefly based upon 

 their name of Nettles, which probably was given them, 

 from a faculty they possessed of stinging, in some measure, 

 like a nettle, a faculty which some of the Medusas are 

 known to possess in a remarkable degree. 1 But Aristotle 

 does not appear to intimate that such an effect follows 

 its touch, except that the fixing of its tentacles caused a 

 swelling. If either of his species is entitled to be con- 

 sidered as a Medusa it must be the smaller; the larger or 

 fixed one appears in one respect to resemble the Amphi- 

 trite magnifica:* they are stated to use the rock to which 

 they are fixed as a shell, whence it should seem that they 



1 The stinging property of many such Tentacula, for instance, 

 in the Medusa and Holothuria, likewise deserves notice. This, 

 which, with some modifications, also exists in several plants, 

 appears to be the lowest degree of the, so called, electric power 

 in several fishes, not recurring in the higher orders of animals, 

 and perhaps comparable as regards man, to the magnetic influ- 

 ence alone. Cams. i. 47. 60. 



- Tubularia maynijica, Linn. Tr. v. 228. t. ix. 



