444 GENERAL INDEX. 



blast compared with an ordinary liydroid medusa, 277 ; its tropliosome indistinguishable from 

 that of Heterocordyle, 294. 



Dictyonema not a graptolite, 184, note. 



Digestion in the Hydroida, 128. 



Dinema of van Beneden not distinct from Perigonimus, 322. 



Dioecious condition of liydroid colony almost universal, 148. 



Diplograptus, a genus of graptolites, 176. 



Discophora, determined by Eschscholfz as a distinct group of the niedusoc, 10 ; fossil impressions of 

 Discophora, 176 ; diagnostic characters of the order, 188. 



Distal end of hydrozoma, 24. 



Distribution of the Hydroida in space; horizontal distribution, 155; bathymetrical distribution, 162; 

 wide distribution of genera, 156; limited distribution of species, 157 ; wide distribution not dependent 

 on production of planoblasts ; distribution of specific forms of hydroid medusae limited,159; distri- 

 bution of the Hydroida in time, 170 ; tabular view of the distribution of the Hydroida in time, 184. 



Dujardin, his observations on the production of medusa" by hydroid trophosomes, 14 ; his account of 

 the development of the eggs in Cladonema, 96 ; his observations on the Cladonema medusa and 

 its development from its trophosome, 96. 



Echer, his views of the structure of Hydra, 123. 



Ectoderm, 21 ; its structure, 110. 



Ectotlicca, 32. 



Edwards, Prof. H. Milne, insists on the distinction between the Hydrozoal and Actinozoal types of 



structure, 11 ; he compares the Flustrse with the compound Ascidians, 11. 

 Ehrenberg, his use of the name Bryozoa as equivalent with the Polyzoa of Thomson, his demonstration 



of the sexuality of the Hydroida, 12; his institution of the genus Eudendrium, 331. 

 Eleutheria, ambulatory gonophore of, 30; distinct from Clavatella, 384. 

 Eleutheroblastea, a sub-order of the Hydroida; characters of this sub-order, 189. 

 Ellis, his researches, 6. 



Ellis and Solandcr, their admirable iconogra])hy, 7. 

 Embryonal development, 85 ; embryonal development in the Hydroida compared with that of the 



Vertebrata, 88. 

 Endoderm,21; its structure, 122; ciliated surface of, 123 and 228; its ridges, 126 ; its condition in the 



hydranth of Tuhnlaria indicisa, 124; its structure in the tentacles of the hydranth, 126; in the 



tentacles of the planoblast, 127. 

 Endostomata of M'Crady, 80. 

 Endotheca, 32. 



Esper, his ' Pflanzenthiere,' 7. 

 Eschscholtz, his recognition of the hydroid medusse as forming a group distinct from that of the 



Discophora, 10. 

 Eudendrium, peculiar condition of its male sporosacs, 45; its male sporosacs compared with Sarsia 



strangidata, 45; atrophy of the hydranth in various species, 236. 

 Euclendrinm ramosum liable to be infested by a parasitic Pycnogonidan, 201 ; incorrectly described by 



authors as having a non-fascicled stem, 333. 

 Eadendrhtin 2n<sillum of Sars probably a Bougainvillia, 319. 

 Evolution of the Hydroida, 230. 

 Exostomata of M'Crady, 80. 



Families of the Hydroida, characters employed in tlicir limitation and diagnosis, 237. 



Fascicled stems, their nature, 262, note. 



Fibrillated tissue, 112 ; in the umbrella and velum, 114; structure of fibrilla? in the tentacles of Tubu- 



laria, 113. 

 Fission, spontaneous, in the medusa; Kolliker's observations on ; in the trophosome, 151 ; in 8chizo- 



cladiiim, 152; probable in Corhnorpha nutans, 153. 

 Forbes, Edward, his division of medustc into Gymnophthalmia and Steganophthalmia ; his monograph 



