. Elementary text-book of zoology. Zoology. HYDEOZOA SIPHONOPIIORA. 247 they are, however, without nianubrium, mouth, tentacles, and sense organs. The deeply concave sub-umbrella surface of the nectocalyx is largely developed and has a very powerful muscular covering in rela- tion to its exclusively locomotive function. All the appendages are developed as buds formed of ectoderm, entoderm, and containing a central cavity which communi- cates with the central space of the stem. In the nectocalyces and gonophores an ecto- dermal ingrowth gives rise to the covering of the sub-umbrella and to the
. Elementary text-book of zoology. Zoology. HYDEOZOA SIPHONOPIIORA. 247 they are, however, without nianubrium, mouth, tentacles, and sense organs. The deeply concave sub-umbrella surface of the nectocalyx is largely developed and has a very powerful muscular covering in rela- tion to its exclusively locomotive function. All the appendages are developed as buds formed of ectoderm, entoderm, and containing a central cavity which communi- cates with the central space of the stem. In the nectocalyces and gonophores an ecto- dermal ingrowth gives rise to the covering of the sub-umbrella and to the generative product.* respectively (fig. 1ST). The ova, of which there is often only one in each female gono- phore, are large, and have no vitelline mem- after im- undergo a regular. brane, and, pregnation, complete and segmentation. A nectocalyx (Diphyes) is the first structure formed in the free-swim- ming larva, or the upper part of the body of the larva gives rise to a cap- shaped protective cover or hydrophy Ilium as well as a pneumato- phore, and the under part becomes the primary nutritive polyp (Ayalmopsis, tig. 188). Since new buds give rise to leaf-shaped hydrophyllia, a small stock with FIG. 190.—Phi/sopJiora hyilruxfatica. Pn, Pneumatophore ; 5, nectocalyces arranged in double rows on the swim- ming column; T, dactylozoid ; P, polyp (nutritive individual) with tentacles, Sf; Kb, groups of nemato- cysts on the latter ; G, clusters of generative Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Claus, Carl, 1835-1899; Sedgwick, Adam, 1854-1913; Sinclair, F. G. (Frederick Granville), b. 1858. New York : Macmillan
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1884
