Zöology; a textbook for colleges and universities . Drawings by W. P. Hay and R. Weber FIG. 115. i, lateral view of an ascidian, and 2, a diagram of its anatomy, a, incur-rent orifice; b, excurrent orifice; c, branchial basket; d, stomach; e, nervous , another species of ascidian (Styda). PROCHORDATA AND CYCLOSTOMES 323 contract, emitting a stream of water. The mouthleads into a large sac, the pharynx, the walls of which nerve ganglion mouth nerve cor notochord. Drawing by W. P. Hay FIG. 116. Diagram of the anatomy of Appendkularia, one of the Larvacea:a, lateral view; b, cross section
Zöology; a textbook for colleges and universities . Drawings by W. P. Hay and R. Weber FIG. 115. i, lateral view of an ascidian, and 2, a diagram of its anatomy, a, incur-rent orifice; b, excurrent orifice; c, branchial basket; d, stomach; e, nervous , another species of ascidian (Styda). PROCHORDATA AND CYCLOSTOMES 323 contract, emitting a stream of water. The mouthleads into a large sac, the pharynx, the walls of which nerve ganglion mouth nerve cor notochord. Drawing by W. P. Hay FIG. 116. Diagram of the anatomy of Appendkularia, one of the Larvacea:a, lateral view; b, cross section of tail. have a more or less latticelike structure, with manysmall openings. This is the gill apparatus, and the waterpassing through it gives up its dissolved oxygen to theblood. At the end of the pharynx is the opening of thealimentary canal. The pelagic or free-swimming Tuni-cata are very different - - more or less cylindrical, andtransparent. Some are quite large, others animals were formerly associated with the Mol-lusca and regarded as a sort of shell-less clams, but theinvestigation of their immature stages showed the entireerror of this view. The larva or young stage is a more The larvalor less tadpolelike creature, with a long tail containing a ^^notochord. In development, all this gradually disap-pears by absorption, except in a group of minute free-swimming forms constituting the class Larvacea, whichretain the elongate form and notochor
Size: 2979px × 839px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1920, booksubjectzoology, bookyear1920
