. Elementary text-book of zoology. Zoology. 246 CffiLEKTEEATA. D The second form of appendage, the gonophores, usually possess a bell-shaped mantle containing circular and radial vessels, and surround- ing the central stalk or clapper (nianubriurn), which is tilled with ova or spermatozoa. They usually arise in clusters at the base of the tentacles, more rarely from the nutritive Polyps themselves ( in Velella}. The male and female generative products always arise separately in differently shaped buds, but are usually found closely approximated on the same stock (fig. 186). There are, howe
. Elementary text-book of zoology. Zoology. 246 CffiLEKTEEATA. D The second form of appendage, the gonophores, usually possess a bell-shaped mantle containing circular and radial vessels, and surround- ing the central stalk or clapper (nianubriurn), which is tilled with ova or spermatozoa. They usually arise in clusters at the base of the tentacles, more rarely from the nutritive Polyps themselves ( in Velella}. The male and female generative products always arise separately in differently shaped buds, but are usually found closely approximated on the same stock (fig. 186). There are, however, also dioecious 812^0- nopliora, or if the niedusoid buds or gonophores be regarded as generative organs, 8i2)hono- pkora of distinct sexes, , Apolemia uvaria and Dipliyes acuminata. The ripe sexual Medusoids frequently become separated from the stock, after the development of the generative products, and only rarely become liberated as small Medusce (Chri/somitra in the relellidffi), which produce generative products during their free life. Besides the constant nutri- tive Polyps and medusoid gonophores, there are incon- stant appendages, which are also modified Polypoids or Medusoids. These are the mouthless worm-like dactylo- zoids (fig. 186), which, like the Polyps, are provided with a tentacle, which is, however, shorter and simpler, and has no lateral branches or aggregations of nematocysts; also the leaf-shaped hard cartilaginous liydropliyllia, which serve to protect the polyps, dactylozoids, and gonophores; and finally the appendages known as nectoccdyces, which are placed beneath the pneumatophore. The nectocalyces have a structure similar to that of the Medusa?, though their bilateral symmetry is apparent;. FIG. 189.—Small larval stock of Agalmopsis after the type of Atlwrybia. Lf, Pneumatophore ; D, hydrophyllhun; Nlc, groups of nemato- cysts ; P, Please note that these images are extracted from scanned page images that may have been digitally
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1884
