150. Comparative diagram of the various modes of bisection of a prismatic sector . . . 365 151. Diagram of the further growth of the two halves of a quadrantal cell . . . 367 152. Diagram of the origin of an epidermic layer of cells . . . 370 153. A discoidal cell dividing into octants . . . 371 154. A germinating spore of _Riccia_ (after Campbell), to shew the manner of space-partitioning in the cellular tissue . . . 372 155, 6. Theoretical arrangement of successive partitions in a discoidal cell . . . 373 157. Sections of a moss-embryo (Kienitz-Gerloff) . . . 374 158. Various possible arrangements of partitions in groups of four to eight cells . . . 375 159. Three modes of partitioning in a system of six cells . . . 376 160, 1. Segmenting eggs of _Trochus_ (Robert), and of _Cynthia_ (Conklin) . . . 377 162. Section of the apical cone of _Salvinia_ (Pringsheim) . . . 377 163, 4. Segmenting eggs of _Pyrosoma_ (Korotneff), and of _Echinus_ (Driesch) . . . 377 165. Segmenting egg of a cephalopod (Watase) . . . 378 166, 7. Eggs segmenting under pressure: of _Echinus_ and _Nereis_ (Driesch), and of a frog (Roux) . . . 378 168. Various arrangements of a group of eight cells on the surface of a frog’s egg (Rauber) . . . 381 169. Diagram of the partitions and interfacial contacts in a system of eight cells . . . 383 170. Various modes of aggregation of eight oil-drops (Roux) . . . 384 171. Forms, or species, of _Asterolampra_ (Greville) . . . 386 172. Diagrammatic section of an alcyonarian polype . . . 387 173, 4. Sections of _Heterophyllia_ (Nicholson and Martin Duncan) . . . 388, 9 175. Diagrammatic section of a ctenophore (_Eucharis_) . . . 391 176, 7. Diagrams of the construction of a Pluteus larva . . . 392, 3 178, 9. Diagrams of the development of stomata, in _Sedum_ and in the hyacinth . . . 394 180. Various spores and pollen-grains (Berthold and others) . . . 396 181. Spore of _Anthoceros_ (Campbell) . . . 397 182, 4, 9. Diagrammatic modes of division of a cell under certain conditions of asymmetry . . . 400–5 183. Development of the embryo of _Sphagnum_ (Campbell) . . . 402 185. The gemma of a moss (_do._) . . . 403 186. The antheridium of _Riccia_ (_do._) . . . 404 187. Section of growing shoot of _Selaginella_, diagrammatic . . . 404 188. An embryo of _Jungermannia_ (Kienitz-Gerloff) . . . 404 190. Development of the sporangium of _Osmunda_ (Bower) . . . 406 191. Embryos of _Phascum_ and of _Adiantum_ (Kienitz-Gerloff) . . . 408 192. A section of _Girardia_ (Goebel) . . . 408 193. An antheridium of _Pteris_ (Strasburger) . . . 409 194. Spicules of _Siphonogorgia_ and _Anthogorgia_ (Studer) . . . 413 195–7. Calcospherites, deposited in white of egg (Harting) . . . 421, 2 198. Sections of the shell of _Mya_ (Carpenter) . . . 422 199. Concretions, or spicules, artificially deposited in cartilage (Harting) . . . 423