Cellularia ciliata, 131.
Cellulose, 252, 267.

Cephalopoda, skeleton of, 336.

Cestum veneris, 190.

Chalk flints, 38.

structure of, 80.

Chara, skeleton of, 172.

Chitine, 386, 405.
Chiton, shell of, 322.
Cidaris, shell of, 216.

spines of, 219, 225.

Cilia in sponges, 12.
Cilio brachiata, 175.
Cilio-grada, 190.

Circulation in sponges, 12.

Cirrhi of Echinoderms, 243.
Cirrhi-grada, 192.

of Star-fishes, 244.

Cirrhipedia, skeleton of, 399.
Cleidotherus chamoides, 306.
Clio borealis, 334.

Coach spring shell, 285.

Coleoptera, skeleton of, 387, 389.
Comatula, 197.

Compound Tunicata, 264.

Conchifera, shell of, 267.

Conjugation of Desmidieæ, 44

Coral, cellular structure of, 173.

reefs, 162.

repair of, 166.

skeleton of, 158.
tubes in, 153.

Corallines, skeleton of, 9, 168.

Corallium rubrum, 127, 129.

Cordylophora, 186.

Coronula, shell of, 402.

Coscinodiscus, 61, 75.
Crabs, shell of, 396.
Cray-fish, shell of, 394.
Crenatula, 297.

Crinoideæ, skeleton of, 196.
Crust of Gorgoniæ, 128.
Crustacea, skeleton of, 391.
Crystalline structure of shell, 304.
Cucumaria, 238.

Cuticle of Deutzia, 9.

Equisetum, 7.

Rice-husk, 8.

Wheat, 8

Cuttle-fish bone, 339.

skeleton of, 338.

Earths, infusorial, 62.
Echinidæ, 213.

Echinocyamus, shell of, 234.
Echinodermata, 195.
Echinus, cirrhi of, 245.
-, repair of spines, 228.
spines of, 220.

teeth of, 232, 234.
Egg shell of ostrich, 205.
Encrinites, 200.

Encrinital marble, 203.
Entomostraca, skeleton of, 391.
Entozoa, skeleton of, 372.
Epidermis of Mussel, 302.

structure of, 328.
Trigonia, 303.

Equisetum, cuticle of, 7.
Eschara cervicornis, 260.

F.

Flints, chalk, 38.

Flustra, skeleton of, 179.
Foraminifera, 77.

method of mounting, 85.

P.

Pachymatisma, gemmules of, 31.
Pamphagus, 108.
Parasitic sponges, 37.
Pavonaria, skeleton of, 136,
spicula of, 139.

Pearl Oyster, 297, 300, 364
Pearls, artificial, 369.

brilliant, 367.

classification of, 365.
nucleus of, 368.
structure of, 359.

Pedicellariæ of Asterias, 210.
Echini, 253.

-, structure of, 251.
Pennatulidæ, 132.
Pennatula grisea, 138.

phosphorea, 134.

spicula of, 138.

Pentacrinus Europæus, 198.

Pentacrinite, 199.

Pentagonaster, 210.

Perforation of Terebratula, 288.

Periostracum, 328.

of shell, 283.

Perna ephippium, 296.

Pholas, shell of, 357.

crispata, shell of, 306.
Phyllosomæ, 393.
Physalia pelagica, 191.
Physograda, skeleton of, 191.
Pinna, shell of, 269, 271.
Pisolite, 93.

Plants, silica in, 6.

skeleton of, 6.

Pleurosigma, 58.

Pollicipes, 400.

Polygastrica, development of, 100.

skeleton of, 98, 111.

Polype, fresh-water, 115.

Polystomella, 77.

Polythalamia, skeleton of, 77.

Polyzoa, 113.

skeleton of, 175.

Poriphera, skeleton of, 11.

Porpita, 187, 192.

Portuna, carapace of, 393.
Prisms of shell, 273.
Proteus, 107.

Pteropoda, skeleton of, 334.
Pulmograda, 187.

Shell, operculum of, 312, 324.
of Oyster, 295, 299.

,

Pearl Oyster, 297, 300, 364.
periostracum of, 283.

Pinna, 269, 271.

Pollicipes, 400.

prisms of, 273.

repair of, 370.
Rice, 276.
Shrimp, 394.
Slug, 268.
Snail, 315.
Spirifer, 280.
Spirula, 343.

Terebratulæ, 284.

Trochus, 319.

tubular structure of, 276.

Shepherd's Purse coralline, 182.
Silica in Plants, 6.

Siliceous Sponge, 17.

Sipunculæ, 254.

Skeleton of Abranchiata, 380.

Acalephæ, 186.

Actiniæ, 154.

Alcyonella stagnorum, 184.

Alcyonium, 144.

Ammonites, 355.

Annelida, 377.

Arachnida, 404.

Articulata, 371.

cellular structure of, 269,

Asteriadæ, 208.