Xll 



LIST OF ILLUSTRATIONS 



FIG. PAGE 



209. Otoliths of plaice, shewing "age-rings" (Wallace) .... 432 



210. Spicules, or calcospherites, of Astrosclera (Lister) .... 436 



211. 2. C- and S-shaped spicules of sponges and holothurians (Sollas and 



Theel) 442 



An amphidisc of Hyalonema 442 



Spicules of calcareous, tetractinellid and hexactinellid sponges, and 



of various holothurians (Haeckel, Schultze, Sollas and Theel) 445-452 

 Diagram of a solid body confined by surface-energy to a liquid 



boundary-film 460 



Astrorhiza limicola and arenaria (Brady) ..... 464 



A nuclear ^'reticulmn plasmatigue'^ (Carnoy) ..... 468 



A spherical radiolarian, Aulonia hexagona (Haeckel) '. . . 469 



Actinomma arcadophorum (do.) ....... 469 



Ethmosphaera conosipJionia (do.) ....... 470 



Portions of shells of Cenosphaera favosa and vesparia (do.) . . 470 

 Aulasfrum triceros (do.) . . . . . . . , .471 



Part of the skeleton of CaniiorhapJ'is (do.) 472 



A Nassellarian skeleton, Callimitra. carolotac (do.) .... 472 



228, 9. Portions of Dictyocha stapedia (do.) 474 



230. Diagram to illustrate the conformation of Callimitra . . . 476 



Skeletons of various radiolarians (Haeckel) 479 



Diagrammatic structure of the skeleton of Doratas2ns (do.) . . 481 



4. Phatnaspis cristata (Haeckel), and a diagram of the same . . 483 



Phractasjris prototypus (Haeckel) ....... 484 



Annular and spiral thickenings in the walls of plant-cells . . 488 



A radiograph of the shell of Nautilus (Green and Gardiner) . . 494 



A spiral foraminifer, Globigerina (Brady) ..... 495 



213. 

 214-7 



218. 



219. 

 220. 

 221. 

 222. 

 223. 

 224. 

 225. 

 226. 

 227. 



231. 

 2,32. 

 233. 

 235. 

 236. 

 237. 

 238. 



239-42. Diagrams to illustrate the development or growth of a logarithmic 



spiral 407-501 



243. A helicoid and a scorpioid cyme ....... 502 



244. An Archimedean spiral 503 



245-7. More diagrams of the development of a logarithmic spiral . . 505, 6 

 248-57. Various diagrams illustrating the mathematical theory of gnomons 508-13 



258. A shell of Haliotis, to shew how each increment of the shell constitutes 



a gnomon to the preexisting structure ..... 514 



259, 60. Spiral foraminifera, Pulvinulina and Cristellaria, to illustrate the 



same principle .......... 514, 5 



261. Another diagram of a logarithmic spiral ..... 517 



262. A diagram of the logarithmic spiral of Nautilus (Moseley) . . 519 



263. 4. Opercula of Turbo and of Ncrita (Moseley) .... 521, 2 



265. A section of the shell of Melo ethiopicus ..... 525 



266. SheUs of Harpa and Dolium, to illustrate generating curves and 



generating spirals ......... 526 



267. D'Orbigny's Helicometer . . ...... 529 



268. Section of a nautiloid shell, to shew the "protoconch" . . . 531 

 269-73. Diagrams of logarithmic spirals, of varioiis angles . . . 532-5 



274, 6, 7. Constructions for determining the angle of a logarithmic spiral 537,8 



275. An ammonite, to shew its corrugated surface -pattern . . . 537 

 278-80. Illustrations of the "angle of retardation" .... 542-4 



