Crystallization, relation of polarization of light and heat to crystallization, i. 70, 71 axes of symmetry of crystals, i. 71, 72 change of position of the optical axes of crystals by heat, i. 72 effect of pressure on the optical axes of crystals, i. 73 influence on the aggregation of, i. 73, 74 probable origin of the crystalline form, i. 74 causes of the variety of forms assumed by matter, i. 74 deviation of dimorphous crystals from the general law of crystallization, i. 75 proof of the connection between the magnetic forces and crystalline structure, i. 76 conditions of the position which crystals take with regard to the magnetic force, i. 76 Crystalloids, or crystalline substances, diffusibility of, i. 109 Crystals, water an essential element in, i. 107 alterations in crystals by heat, i. 108 Cunina octonaria, larvæ of, parasites of the Turritopsis nutricula, ii. 100 Cusconine, structure of, and whence obtained, i. 427 Cuthbert’s, St., beads, ii. 175 Cutaneous diseases caused by fungi, i. 274 Cutleria multifida, structure, mode of reproduction, and habitat of, i. 248 Cuttle fish, structure of the, ii. 245-247 Cyanogen, combines with other substances and simple atoms, as if it were a simple element, i. 106 combination forming it, i. 106 Cyathea medullaris, used as food in New Zealand, i. 360 Cyatheæ, structure of, i. 360 Cyatheineæ, characters of the group, i. 344 sporangia of, i. 343 structure and fructification of, i. 360 Cycloclypeus, structure and habitat of, ii. 48 Cyclops quadricornis, structure and mode of reproduction of, ii. 205, 206 Cydippe pileus, structure of, ii. 101, 102 Cymothea, their food and mode of taking it, ii. 203 Cyprææ, or cowries, shells of, ii. 234, 235 Cypris, structure and mode of reproduction of, ii. 207, 208 Cystopteris, characters and habitat of the genus, i. 348, 349 Cystopus candidus, or Uredo candida, structure, habitat, and mode of reproduction of, i. 278 Cystopteris fragilis, or brittle bladder fern, structure and habitat of, i. 349 Cystoseira, structure and habitat of, i. 255 Cystoseireæ, habitat of, i. 255 Cyttaria, the food of the Fuegians, i. 292 habitat of the, i. 292 D Dactylocalyx pumiceus, spicula and skeleton of, ii. 60 Daphnia pulex, or arborescent water-flea, structure and mode of reproduction of, ii. 208 Dasya, structure of, i. 241, 242 Dasyglœa, structure of, i. 215 Datura sanguinea, intoxicating effect produced by a drink obtained from, i. 427 Davallia canariensis, or hare’s-foot fern, i. 351 Davallieæ, structure and habitat of, i. 350, 351 Dead bodies, agents in the decomposition of our, ii. 67 Decapoda, structure of, ii. 245 Decapods, tribes of the, ii. 188 characters of the, ii. 189 Delesseria alata, structure of, i. 243 Delesseria angustissima, structure of, i. 243