56 MORPHOLOGY. 



that Loveii long ago^ called attention when he supported and developed the doctrine, just then 

 announced by Ehrenberg, of the sexuality of the Hydroida — a doctrine which, though in its 

 mode of statement not aljsolutely correct, was yet fidl of significance. 



The bodies {(],(/') in question are nearly spherical sacs, and occur in both the male and female 

 colonies. In their walls may be demonstrated an ectotheca, mesotheca, and endotheca. The 

 generative elements are formed within the endotheca, and surround a well-developed spadix. 

 The endotheca, however, is generally of short duration, becoming absorbed or ruptured under the 

 increasing volume of its contents. In the female four very distinct radiating canals may fre- 

 quently be seen ; these spring from the base of the spadix, and thence run in the walls of the 

 mesotheca towards the opposite end of the sac. In many cases, however, I was unable to 

 detect any trace of these canals, and could never find them in the male. We should, however, 

 be scarcely justified in asserting that in such cases they are altogether absent ; for it is quite 

 possible tliat emptiness or some other peculiar condition at the time of observation may have 

 caused them to escape detection — a supposition which receives confirmation from the fact that, 

 even in cases where they are obvious, they become obliterated under slight pressure. 



At the summit of the sac the mesotheca is perforated by a circular aperture, round which 

 its walls appear to be thickened, and seem to contain here a circular canal in which the radiating 

 canals terminate ; at least, the presence of a line of coloured granules at this place affords an 

 indication of the existence of such a canal. The ectotheca, which is loaded with thread-cells, is also 

 perforated by an aperture corresponding to that of the mesotheca; and the gonophore is crowned 

 by a circle of short tentacles, which seem to originate from the thickened margin of the perfo- 

 ration in the sunmiit of the mesotheca. 



These tentacles possess, like the marginal tentacles of a true medusa, considerable con- 

 tractility. They may frequently be seen of very different lengths in different gonophores of the 

 same colony ; and this, which is really the result of different degrees of contraction, may be 

 easily taken for different degrees of development, the tentacles being especially sluggish in the 

 acts of extension and contraction. Their length, when fully extended in the female gonophore, 

 will equal about half the diameter of the gonophore. While under external irritation, they will 

 slowly contract to a third of their original length, and will then show themselves as a little 

 stellate crown on the summit of the gonophore, reminding us of the sessile stigma in the pistil 



diagnosis than was possible so long as we were ignorant of the true nature of this curious hydroid, and 

 the following may be taken as expressing the essential characters of the genus : 



CoppiNiA, Hassall. 



Trophosome. — Hydrocaulus absent ; hydrothecoe tubiform, springing from an adherent retiforra 

 hydrorhiza. 



Hydranths with a single verticil of filiform tentacles. 



Gonosome. — Gouosphores adelocodonic ; gonangia tubiform, sessile on the hydrorhiza, aud forming, 

 by the close approximation of their sides, a continuous incrusting mass surrounding the bases of the 

 hydrothecte which project from it at intervals. 



^ Loven, " Beitrage zur Kenntniss der Gattungen Campanuluria und Sijncoryne ,''' 'Wiegm. Arch., 

 1837. Loven names the hydroid in which he witnessed the extracapsular gonophores Campamdaria 

 geniculala, which is certainly a wrong determination of the species. See " Notes on the Hydroida," 

 'Ann. Nat. Hist.' for August, 1859. 



