448 GENERAL INDEX. 



Noj'thern Atlanto-Amevican province, 162. 

 NulHpores, their vegetality maintained by Cavolini, S. 



Obelia, structure of umbrella in, 11.5; supposed nerve-cord in, 1.38. 



Oceania armata, development of the eggs in, 97. 



Ocellus, -33; its structure and situation, 138; lens-like body occasionally occurs in it, 139; its supposed 



function, 139. 

 Oldhamia, not properly a hydroid, possibly inorganic, its form and geological area, 171. 

 Ophiodes, peculiar appendages in, 28. 

 Orientation of the hydroid, 24. 

 Ovum, hydroid, its structure, 64; development of, 8-5 ; special features in the development of ovum in 



Tubularia, 90; in Hydra, 94; ova in the blastostyle of Scrtularia jnimila, 150. 



Pallas, his ' Elenchus Zoophytorum ;' he adopts the binomial nomenclature of Linna-us, 6 ; he describes 



a Coryne and a CUava, 7. 

 Pahroeoryne, description of, by MM. Duncan and .Jenkins ; no sufficient grounds for regarding it as a 



hydroid, 172; probably a rhizopod, 173. 

 Palagina. gigantea, fossil hydroid medusa of the Solenhofen slate, 175. 

 Palpocils, 111. 



Parypha, a sub-genus of Tubularia, 399 and 416. 

 Parasitic pichnogonidan, 200. 



Pennaria exceptional among the Gymnoblastea in the distichous disposition of its branches, 305. 

 Pennaria Cavolinii, its medusa attains to sexual maturity without liberation, 366. 

 Pennarta gibhosa, the fusiform swellings of its radiating canals not to be confounded with generative 



sacs, 367. 

 Perisarc, 26; a product of the ectoderm, 135. 

 Perigonium, 32. 



Peron and Lesueur, their Australian voyage, 8. 

 Peyronelle demonstrates the animality of corals, 5. 

 Phanerocodonic gonophores, 30. 

 Phosphorescence in the trophosome ; in the planoblast ; manifested under the operation of a stimulus; 



action of alcohol on; emission of light by marginal bulbs of medusoe, 145; phosphorescence in 



Beroe requires previous seclusion in darkness, 146, note. 

 Phoxichilklium coccineum, a parasite o( Si/nconjnc ezhnia, 201. 

 Phyllograptus an anomalous graptolitic form, 177. 

 Physiognomy of the Hydroida, 1. 

 Physioiogy of the Hydroida, 128. 

 Pichnogonidffi parasitic in hydroids, 200. 

 Planoblasts, 29. 



Planula, 88 ; development of, 89. 

 Plumularians, gigantic, 156. 



Podocoryne carnea, sexual maturity of its medusa occasionally noticed before liberation, 350. 

 Podocorync prohoscidea, sexual maturity of its medusa before liberation, 351. 

 Polarity of the hydroid, 70. 

 Polype, use of this term, 24. 

 Polypi te, use of this term, 24. 

 Porcupine Expedition, hydroids obtained by it from great depths ; its discovery of the deep cold 



North Atlantic area, 165 ; it discovery of abyssal forms of liydroids, 165, 170. 

 Protohydra, account of, by Greef, 230. 

 Protoplasm of nematophores, 115. (See Sarcode.) 



Provinces of hydroid distribution, 161; Boreo-Celtic province; northern Atlanto-American province; 

 West Indian province ; North Pacific province ; Australian province ; New Zealand province, 162. 

 Proximal end of hydrosoma, 24. 

 Quatrefiges, !M. de, his memoir on Hydractinia (Synhydra), 343 ; his memoir on Eleutheria, 384. 



