Elementary text-book of zoology, tr Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote elementarytextbo01clau Year: 1892-1893 PORIFEHA. 217 Amongst the calcareous Sponges, the simple Sponge with inhalent pores and terminal osculurn (Olynthus-fown) is represented by the stock-forming Leucosolenia (Grantiu), which is composed of numerous hollow cylinders. The structure of this sponge has been described by Lieberkiihn. In the Syconidoe the body cavity has a more complicated form. The central space opens into secondary peripheral spaces or radial
Elementary text-book of zoology, tr Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote elementarytextbo01clau Year: 1892-1893 PORIFEHA. 217 Amongst the calcareous Sponges, the simple Sponge with inhalent pores and terminal osculurn (Olynthus-fown) is represented by the stock-forming Leucosolenia (Grantiu), which is composed of numerous hollow cylinders. The structure of this sponge has been described by Lieberkiihn. In the Syconidoe the body cavity has a more complicated form. The central space opens into secondary peripheral spaces or radial tubes, which are lined by ciliated cells, and open externally through the inhalent pores (fig. 162). In other calcareous Sponges (Leuconidcc] the radial canals have the form of irregular parietal canals, giving oft* branches to the periphery and possessing dilated, ciliated chambers. This form of internal canal system is also found in most of the stock-forming, silicions Sponges (fig. 163). Sponge forms may become more complicated by the formation of stocks ; the originally simple Sponge, which has developed from a single cili- ated larva, gives rise by budding and incomplete fission to a polyzoid sponge body; or several originally separate individu - als, each of which has origi- nated from a single larva, fuse together to form a com- pound sponge stock. Both these methods of growth are repeated in a similar manner in the formation of the stocks of Polyps (fig. 164). In the same way that the fan-like FlG. 163.—Section of Curticium candelabrum (after nets of the Fan C'ul'al (//////'/- JFr. E. Schulze). <Jk, Ciliated chamber of tbr / /» j ij \ i parietal canal. dogwgw. JlaMlum) are formed by the repeated fusion of its branches, the gastrovascular cavities of which anastomose, so also in the case of the branching sponges, as a result of the same pro- cess, reticulate, or coiled or even massive stocks are formed (fig. 165).
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