450 GENERAL INDEX. 



Synthcciiim, origin of gonaiigium within the hydrotheca of, 229. 



Teutacula, their variations, 25 ; structure of their endoderm in the liydraiuli, 12.J ; and in the piano- 

 blast, 127. 



Teratology of the Hydroida, 200. 



Thamnocnidia, a sub-genus of Tubularia, 399 and 406. 



Thompson, J. v., he recognises the essential structure of the Polyzoa ; his employment of the name 

 I'olyzoa, 11. 



Thread-cells, their structure and mode of action, 118 ; their form in Gemmaria implexa, 119; observa- 

 tions of Moebius on, 120; of Mr. Lewes on, 229; their evolution a physical act, 121; their 

 development, 122 ; their formations, 128, 229. 



Thuiaria articulata, its great bathymetrical range, 165. 



Traropsis, development of the egg in, 98; ocellus-like pigment-spot in, 139. 



Timaformosa, development of eggs in, observed by Alex. Agassiz, 97. 



Touch, sense of, its seat, 144. 



Trachynema ciliatum, Gegenbaur's account of its development, 80. 



Trachynemites deperdita, a fossil hydroid medusa of the Upper Jurassic strata, 174. 



Trophosome, 23. 



Tubularia, its animality first demonstrated by Bernard de .Jussieu, 5 ; development of ovum in, 90 ; 

 endoderm of hydranth in, 124; canalliculation of endoderm in, 124; dismemberment of the 

 genus by Agassiz, 399 ; provisional species of Tubularia, 420. 



Tubularia indieisa, -Aimtomy of; structure of its stem; structure of its hydranth, 205; fibrillated tissue in 

 its tentacles, 206 ; structure of its gonophores, 207. 



Tuhdaria mesembryanthemum, tubular processes of its spadix ; structure of its stem ; irritability of its 

 hydranth, 420. 



Tubularia rcgalis, great size of its hydranth ; its high northern area, 405. 



Turris, development of the egg in, 97. 



Umbrella of planoblast, 33; its structure, 113; epithelial layers in, 113; fibrillated tissue in, 114; its 

 structure in Obelia, 115; its ofRce in locomotion, 136. 



Vegetation, marine, its relation to the bathymetrical distribution of animals, 164. 

 Velum, 33 ; fibrillated tissue in, 114; its oflice in locomotion, 136. 

 Vogt, Carl, his group of the Hydro-medusse, 15. 



Wagner, Rud., describes the production of eggs by the medusiform buds of his " Hydra {Podocoryne) 

 aculeata," 342. 



Wehstcria crisioides, fossil of the London Clay, possibly a hydroid, 174, 7iote. 



West Indian province, 163. 



Wright, Dr. Strethill, observes the development of the eggs in Turris, 97 ; in T/nii/ma/ilias i/icoaspicua, 

 97; observes the development of the planula in Zygodactyla, 97; describes palpocils. 111 ; spiral 

 zooids of Hydractinia first described by him, 223 ; describes certain filiform appendages in 

 Hydractinia; describes the canalliculation of the stem in Tuhtdariaindivisa, 125; distinguishes a 

 scattered from a clustered form of Clava, 247 ; his revison of the genus Eudendrium and institu- 

 tion of the genus Atractylis, 299. 



Yolk, cleavage of, in the Hydroida, 87 ; its differentiation round the germinal vesicle, 149. 



Zoantharia, diagnostic characters of the, 188. 



Zoography, hydroid, general principles of, 235. 



Zooid, definition of tliis term, 22, tiote ; genetic succession of zooids, 101. 



Zooidal and embryonal multiplication in the Hydroida, relation between these, 101. 



Zones of depth, 163. 



Zygodactyla, development of planula in, 97. 



