INDEX. 285 



Infusoria : groups of, of opposite characters in the same liquid, ii. 66 



the agents in the decomposition of animal matter, ii. 67 



minuteness of the ferments, ii. 68 



cilia of Infusoria, ii. 68 



as organs of locomotion, ii. 69 



cell constituting the body of Infusoria, ii. 70 



food and organs of digestion of, ii. 70 



transparent contractile vesicles, ii. 71 



modes of propagation, ii. 74 et seq. 



in a state analogous to hybernation, ii. 78, 79 



functions assigned to Infusoria in the economy of nature, ii. 79 

 Insects, phosphorescence of, i. 167 



Intelligence, or the mental principle, of animals, ii. 11, 12 

 Iodine, i. 18, 21 



whence obtained, i. 19 



properties of, i. 21, 22 



spectrum of, i. 21 



atomic weight of, compared with that of hydrogen, i. 100 



preparation of, from sea -weeds, i. 128 



spectrum analysis of, i. 140, 141 



iodine richer at Guernsey than elsewhere, i. 258 

 Iris germanica, vertical section showing the cellular tissue of, i. 173 

 Iron heated by percussion or impetus, i. 27 



effect of electricity on, i. 32 



effect of magnetism of, i. 75, 76, 77 



and of heat on the magnetism of, i. 77 



feeble affinity of iron for mercury, i. 98 



atomic weight of, compared with that of hydrogen, i. 100 



spectrum analysis of the rarefied vapour of, i. 142 

 Isaria, its structure and habitat, i. 282 



its destruction of caterpillars, i. 282, 293 

 Isaria crassa, characters of, i. 283 

 Isaria farinosa, characters of, i. 283 

 Isariacei, structure and habitat of, i. 282 

 Isidae, structure, habitat, and mode of reproduction of, ii. 125 

 Isis, structure of the genus, ii. 125 

 Isomeric substances, i. 104 



law of the sequence of three isomeric bodies, and their respective 



atomic numbers, i. 105 



Isomorphism, property of, in determining atomic weights, i. 99 

 Isomorphous substances, conduct of, under magnetic influence, i. 76 

 Isopoda, characters of the order, ii. 202 



