338 



HYDROID^. 



Part IV. 



1st Sub-order. RUGOS^E. — Coralliaria Rugosa 3Iihic-Edw. and Haiine ; with four 

 families : Staurida^, Cyathaxonidte, Cyathophyllida^, and Cystiiiliyllidae ; all ex- 

 tinct, and mostly belonging to the earliest geological periods, for the enu- 

 meration of which I refer to the elaborate works of Milne-Edwards and 

 Haime. Evidently the Hydroid elements prevailed in the structure of these 

 animals, and they probably never produced Medusoid buds. How far the 

 living types of Hydra and Lucernaria may be related to them still remains 

 to be ascertained. 



2d Sub-order. TABULATE. — Coralliaria Tabvilata Milne-Edw. and Haime; with 

 four families : Milleporidoe, Seriatoporida?,^ Favositidse, and Thecida?, for the 

 characteristics of which I refer to the papers of Milne-Edwards and Haime. 

 The Tubulosa Milne-Edw. and Haime, seem to me to be low forms of Tabu- 

 lata. Should Millepora prove to produce medusae-buds, I would not hesitate 

 to unite this sub-order with the following. 



3d Sub-order. TUBULARI^.^ Alternate generations. Hydra always pedun- 

 culated, and mostly attached, head more or less club-shaped, without distinct 

 horny bell ; Medusa, either free or sessile, deep bell-shaped, with few hollow 

 tentacles, all, or at least the most prominent of which, are in the prolong- 

 ation of the radiating chymiferous tubes ; eyes never independent of the 

 tentacles. Reproductive organs always connected Avith the proboscis, and 

 never limited to the radiating chymiferous tubes. 

 1st Family. Clavid.e IlcCradij? 

 Clava Gmcl — ^QQ p. 218. 



C. multicornis Jolimi. — Clava parasitica Gmel. — Coryne squamata 

 Z?«Z-., VanBen. — 3fedite?ranea7i (Forskal) ; British Channel {VaWixs). 

 C. leptostyla Ag., PL 21. — 3£assachuseUs Buy (Agassiz). 



' I have shown, p. 29G, that in Seriatopora the 

 same tendency to a quadripartite division of the 

 cells prevails, as among the Rugosa, which indicates 

 a closer relation between the Tabulata and Ru- 

 gosa than Milne-Edwards seems to admit. 



"^ Lamouroux, ignorant of the mode of growth 

 and reproduction of these animals, included onh' 

 Hydroids in this group, to which many free Me- 

 dusae are now also referred. It is highly impor- 

 tant to notice the close affinities which bind together 

 the Medusas of this sub-order, and the Hydroids 

 from which they arise. We shall see that these 

 relations are most intimate in all the minor nat- 



ural groups of these Acalephs, the Medusa and 

 Hydra of which are equally well known. 



* The simple, uniform tentacles, scattered upon 

 a club-shaped head, and the sessile medusas-buds, 

 characterize this fiimily. The extraordinary changes 

 which the proboscis assumes (PI. XXL), show 

 that the peculiar arrangement of the tentacles, in 

 the Tubularida^ belongs to the same series. The 

 Tubularians present, in fact, a beautiful gradation 

 of forms, indicating a large number of distinct fam- 

 ilies. In Clavida?, the head of the Hydra- is 

 simply club-shaped, and all the Hydra; of a com- 

 munity are alike, and so are they in Sarsiada; ; 



