. A manual of zoology. Zoology. IV. VERTEBRATA 449 a blind tube, surrounded by tough membrane and thickened beneath, which extends from the pharynx into the proboscis. Embryology throws little light on the problem. Some species have a direct development (fig. 507, B, C), while others have a larva {Tornarla, A) which so resembles the larvae of certain echino- derms that it was long held to belong to that phylum. The chief resemblances are in the relations of the ciliated bands to the alimentary tract and in the pres- ence of the proboscis cavity, which, like the amljulacral system, opens to the
. A manual of zoology. Zoology. IV. VERTEBRATA 449 a blind tube, surrounded by tough membrane and thickened beneath, which extends from the pharynx into the proboscis. Embryology throws little light on the problem. Some species have a direct development (fig. 507, B, C), while others have a larva {Tornarla, A) which so resembles the larvae of certain echino- derms that it was long held to belong to that phylum. The chief resemblances are in the relations of the ciliated bands to the alimentary tract and in the pres- ence of the proboscis cavity, which, like the amljulacral system, opens to the exterior. The old genus Balano- glossus* has recently been sub- divided. Two deep-sea forms, Cephalodisais and Rhahdoplcnra, have the same type of 'notochord,' and the first has a pair of gill slits; in other respects these are strikingly Polyzoan in appearance. Sub Phylum IV. Vertebrata. In the vertebrates only the internal segmentation occurs. This is shown most clearly in the lower \'ertebrata, in the muscles (myotomes, myomeres), the myosepta wdiicli separate them, and the protovertebnc from. 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 Hertwig, Richard, 1850-1937; Kingsley, J. S. (John Sterling), 1854-1929, ed. and tr. New York, H. Holt
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectzoology, bookyear1912
