. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. niDROZOA— 247 they are, however, without manubrium, 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 ara developed as buds fornif-J of ectoderm and endo- d?rm, and containing a central cavity which communicates with the central space of the stem. In the iiectocalyces anl gonophores an ecto- dermal i
. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. niDROZOA— 247 they are, however, without manubrium, 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 ara developed as buds fornif-J of ectoderm and endo- d?rm, and containing a central cavity which communicates with the central space of the stem. In the iiectocalyces anl gonophores an ecto- dermal ingrowth gives rise to the covering of the sub-umbrella and to the generative products respectively v(fig. 187). The ova, of which there is often, only one in each female gono- phore, are large, and have no vitelline mem- brane, and, after im- pregnation, undergo a complete and regular 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 hydrophyllium as well as a pneumato- phore, and the unde?' part becomes the primary nutritive polyp (Ayalmopsis, fig. 188). Since new buds give rise to leaf-shaped hydrophyllia, a small stock with. FIG. 190.—Physoplwra JiydroK/uficrr. Pn, Pnemnatophcre ; S, nectocalyces arranged in double rows on the swim- ming column ; T, dactylozoid ; P, polyp (nutritive individual) with tentacles, Sf; Nk, 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. London, Swan Sonnenschein & co.
Size: 1063px × 2351px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., book, bookcentury1800, bookcollectionbiodiversity, bookdecade1890
