. Elementary text-book of zoology. Zoology. TETHYODEA. 91 Eml distance from the mouth a circle of usually simple tentacles. On the neural side of the branchial sac is the cloacal cavity which receives not only the water flowing out through the branchial slits, but also the faeces and the generative products. The digestive canal, together with the other viscera, is some- times placed as in all the simple Ascidians rather to the side of the branchial sac or, as in the elongated forms of the compound Ascidians, simply behind the same, and in the latter case often occasions a constriction of the b
. Elementary text-book of zoology. Zoology. TETHYODEA. 91 Eml distance from the mouth a circle of usually simple tentacles. On the neural side of the branchial sac is the cloacal cavity which receives not only the water flowing out through the branchial slits, but also the faeces and the generative products. The digestive canal, together with the other viscera, is some- times placed as in all the simple Ascidians rather to the side of the branchial sac or, as in the elongated forms of the compound Ascidians, simply behind the same, and in the latter case often occasions a constriction of the body, so that Milne Edwards was able to distinguish a thorax and abdomen, or even a thorax, abdomen and post-abdomen. The Ascidians either remain solitary, and then usually attain a considerable size (A. solitarice), or by budding and throwing out root-processes they produce branched colonies, the individuals of which are connected together by their body walls, and are not embedded in a common mantle covering (A. societies). In other cases (Synascidice) numerous in- dividuals live in a common man- tle ; they often have a charac- teristic around a common central opening (A. composites), so that each group has its central cavity, into which the exhalent ( atrial) openings lead as into a common cloacal cavity (fig. 561). There are solitary (Appendicularia) as well arrangement. FIG. 560.—Clacellina lepadiformig (regne ani- mal), somewhat diagrammatic. &, Mouth; Br, branchiae ; End, endostyle ; Oe, oesophagus ; G, nervous centre ; MD, stomach ; Kl, cloacal chamber; A, exhaleut pore; Af, anus; GD, genital gland ; Off, duct of genital gland ; Sf, stolons. as compound Ascidians (Pyrosoma) which can move freely. The solitary Appendicularice execute the most perfect swimming move- ments. In their external form they resemble the free-swimming Ascidian larva?, and like these they have a whip-like swimming. Please note that these images are extracted from scanned page images that m
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1884
