76 THE OCEANIC HYDROZOA. 



The nectosac has a comparatively narrow, oval, or rounded aperture, fringed by the 

 usual valvular membrane. Its cavity near the aperture is suljcylinth'ical, gradually widening 

 internally. It then suddenly dilates, and forms a very wide, blind, sac, more or less divided 

 into two lobes by a median constriction. The cavity is much wider than it is deep. 



Below the nectocalyces four thick and solid hydrophjdlia are attached, so as to lie nearly 

 in the same plane. They have the form of pyramidal wedges, with square bases.^ The 

 latter are turned outwards, while the apices are connected with the coenosarc by a duct which 

 extends, as a caecal phyllocyst, through the axis of the hydrophyllium, terminating at some 

 distance from its base. In some specimens there was a second set of such appendages, but 

 in others, these hydrophyllia were succeeded by four different ones, much larger and more 

 foHaceous, though still very thick. Internally, they are concave ; superiorly, convex. Exter- 

 nally, they present two or more somewhat excavated facets, separated by thick ridges. Their 

 lateral edges are sharp, and coarsely serrate, and they taper more or less to a point below. 

 Like the preceding, these organs contain long and narrow caecal phyllocysts, which traverse 

 their axes, and nearly reach their apices. 



The polypites lie amongst and between the hydrophyllia. Bunches of what appear to 

 be young polypites (hydrocysts), accompanied by rudimentary hydrophyllia and tentacles, are 

 attached to the coenosarc, between the fully formed ones, and are either on the same pedicle 

 with, or close to, the reproductive organs. 



The sacculi of the tentacula are nearly a sixth of an inch long, and possess a long 

 median prolongation or lobe, flanked on each side by a filament of about double its length. 

 The involucrum is very large, and apparently capable of containing the whole sacculus. 



The reproductive organs are developed more particularly towards the lower end of the 

 coenosarc, the male and female organs being placed close to one another. The gynophores 

 are very numerous, and about half as large as the androphores, which are fewer in number. 

 The gynophores are borne upon special stems, or gonoblastidia, each of which is simply a 

 process of the coenosarc, and contains, of course, a diverticulum of the somatic cavity. On all 

 sides the gonoblastidium gives off short bud-like processes, wliose development is always the 

 more advanced the nearer they are to the free end. It would appear, therefore, that new 

 ones are continually developed at the base of the gonoblastidium. The smallest of these pro- 

 cesses is a mere caecal process of the endoderm and ectoderm, and is rather less than jijth of 

 an inch in length. It next becomes pyriform, and the endoderm acquires so great a thickness 

 at the apex and at the neck of the organ, that the included cavity assumes a more spherical 

 form, with a narrower neck. The thickened apical endoderm now presents a clear space of 

 about T5^th of an inch in diameter, containing a spheroidal, pale, solid body. These are the 

 rudiments of the germinal vesicle and spot. 



The largest gynophores are oval bodies, attached by a short pedicle, and about -^^th of 



^ la describing his Agalma Okenii Eschscholz states that, of tlie solid, cartilaginous pieces, 

 " some are similar to a very depressed pyramid, whose base presents two longer and two shorter sides. 

 The broader lateral faces meet at the apex of the pyramid earlier than those which ascend from 

 the narrower sides. Other pieces are very irregular ; they present a broad base, then a large, convex 

 surface, and many small excavated cues, which cause one side of the piece to be notched [zackig)." 

 Figs. 1 e, ] / of pi. xiii, which represent these solid pieces, have a close resemblance to mine. 



