850 Prof. Allman on the Construction and 
defined in the present paper; the “ ccenosare” is the common 
connecting basis of the colony, and is more or less completely 
invested by a chitinous “ periderm” excreted from its surface ; 
the “ hydrorhiza” (Huxley) is the root-like proximal termination 
of the ccenosare by which the Hydroid attaches itself to foreign 
bodies; the “hydrocaulus” is the free or (in certain creeping 
forms) more or less adherent portion of the coenosarc, which 
intervenes between the hydrorhiza and the polypites ; the “ meta- 
stome”’ is that portion of the polypite which intervenes between 
the mouth and the most distal set of tentacles; the “ hydro- 
theca” (Huxley) is the cup-like receptacle into which the polypites 
are retractile in the Campanularian and Sertularian Hydroids; 
the “ gonophore” is the proper generative bud, either in the 
form of a sac or of a locomotive Medusa, upon which devolves 
the function of giving origin directly or indirectly to the gene- 
rative elements; the “ gonangium” is the capsule or receptacle 
in which the gonophores are contained in the Campanularian 
and Sertularian Hydroids; the “ gonoblastidium ”’ (Huxley) is a 
more or less developed column which exists in certain Hydroids, 
and is destined to give origin to the gonophores, which are pro- 
duced as buds from its sides; “adelocodonic” gonophores are 
those which are constructed on the plan of the “ sporosac”— 
that is, in which the umbrella is never developed so as to pre- 
sent a wide orifice or “ codonostome,” and never becomes capa- 
ble of acting as a locomotive organ ; ‘ phanerocodonic” gono- 
phores are those which present the type of the developed Me- 
dusa in which the umbrella presents a wide orifice, and may in 
almost every case act as an organ of locomotion. 
I. 
Synopsis of the Genera and Species of Tubularian Hydroids 
whose trophosomes are known. 
Clavide. 
1. Crava, Gmelin. 
Trophosome.—Ccenosare consisting mainly of a filiform hydro- 
rhiza entirely invested by a chitinous periderm; hydrocaulus 
rudimental, and consisting of very short, simple, tubular pro- 
cesses from the free surface of the hydrorhiza, invested, like the 
hydrorhiza, by a periderm, and carrying the polypites on their 
summit. Polypites claviform, with scattered filiform tentacula. 
Gonosome.—Gonophores adelocodonic, sessile or on very short 
peduncles, borne on the body of the polypite at the proximal 
side of the tentacles. 
Clava multicornis, Forskal (sp.), = Hydra multicornis, Forskal. 
Clava repens, Wright, = Clava discreta, Allm. 
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