INDEX 



465 



Sexual differentiation, 



pCOl>, control by, 



fails to induce alone, 349 

 levels inducing, 348 



pH, importance of, 350, 354 



pNH:,, importance of, 349, 354 



pO-, importance of, 354 



population density on, 354 



rhythmicity of, 363-372 



shaking on, 343, 354 



of a single hydra, 344 



size of hydra on, 354 



species of hydra on, 354, 368 



stagnation on, 347, 354 



surface/volume ratio on, 347, 354 



temperature on, 354 



time of year on, 358 



variation in periods of, 366 



versene on, 354 



vessel, importance of shape on, 354 



viscosity of culture solution on, 354 

 Sexual hydra, 



appearance of, 363 



percentage of, 364 



see also Sexual differentiation 

 Side branch, of Cordylophorci, 290-292 

 Skeletogenesis, in corals, 272 



see also Calcification 

 Skin, human, 



aging of, 378 



section of, 377 

 Slime molds, feedback factors, on aggre- 

 gation of, 357 

 Snap-fastener relationship, of ectoderm, 



8 

 Sodium, 



on hydra development, 204 



on hydra growth, 204 



inhibits feeding reflex, 215 



requirement for, 204 

 Splierules de reserves, 326 

 Spindle bridge, 46 

 Spindle filaments, 46, 80, 94 

 Spindle remnant, 46 

 Spines, of nematocvst tube, 84, 86, 132, 



134 



bulbous enlargements of, 134. 138 

 Spiral zooids, 



of Hijdractinia, 356 



of Fodoconjne, 356 

 Spirocysts, 188 



discharge of, 194 



equated with nematocysts, 188 



function of, 188 



structure of, 188 



Sponges, in reef building, 270 

 Stagnation, 348, 360, 361 



influence on halo zone, 340 



on sexual differentiation, 335 

 Starvation, 



on C. viridissima, 262 



on differentiation, 335 

 Stems, of CordylopJiora, 287 

 Stenotele, 84, 86, 114, 120, 131-151, 189 



capsule of, 132 



discharge of, 149-151 



head, of tubule, 132, 134 



hook of, 132 



invaginated capsule of, 132 



mechanism of discharge, 133 



operculum of, 132, 134 



role of, 194 



spines of, 132, 134 



structure of, 85, 131, 132 



stvlets of, 132, 134 



tubule of, 132, 133 



see also Nematocyst 

 Strobilization, 



of Amelia, 336 



of Ctjanea artica, 335, 336 



factors influencing, 336 

 Stoichactis, nematocyst discharge in, 201 

 Stolons, of Cordijlophora, 287-292 



spacing of, 290 

 Stolonizing hydra, 268 

 Stolons, secondary, 290, 292 

 Stomocnidae, 188, 189, 195 

 Stylets, of stenotele, 132, 134 



interlocking, 142 

 Subepithelial hair, 70 

 Succinoxidase activity, in hydra homoge- 



nates, 155 

 Succinoxidase chain, 160 

 Succinoxidase inhibitor, from hydra 



see Inhibitor, of succinoxidase aeti\'ity 

 Supporting structure, of cnidocil, 144 

 Siuface, 



of digestive cell, 20 



of ectoderm, 12 



of epithelio-muscular cells, 2 



of hypostome, 34 



of pedal disk, 40 

 Symbiosis, 255-268 



in A. clegantissima, 255-258 



in C viridissima, 259-268 



in corals, 271 



on regeneration, 404 



zoochlorellae, possible role of, 262 



