. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. The simplest form of Ascidian test is that presented by the Salpae. Here, we have merely a gradual growth of the periplast and a deposit of cellulose within it, the endoplasts either remaining as such or becoming sur- rounded by cell walls. The resulting tissue, in fact, is identical with cartilage, if we suppose cellulose to have taken the place of chondrin. In the Pyrosomata, the test has a struc- ture which, on the one hand, resembles bone, on the other some forms of fibre-carti- lage. The endoplasts, in fact, have be
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. The simplest form of Ascidian test is that presented by the Salpae. Here, we have merely a gradual growth of the periplast and a deposit of cellulose within it, the endoplasts either remaining as such or becoming sur- rounded by cell walls. The resulting tissue, in fact, is identical with cartilage, if we suppose cellulose to have taken the place of chondrin. In the Pyrosomata, the test has a struc- ture which, on the one hand, resembles bone, on the other some forms of fibre-carti- lage. The endoplasts, in fact, have become surrounded by cell walls, which are produced into long, frequently anastomosing processes (./%. 314. D) ; these retain their animal com- position, while all the immediate tissue is strongly impregnated with cellulose. This is the fundamental structure of the test in the Phailusiae and Clavelinas also; but here an additional complication results from the development in the substance of the test of a series of rounded cavities, which gradu- ally enlarge until they almost come into con- tact, and give rise to a spongy texture. The intervening septa at the same time frequently become obscurely fibrous (Jig. 314. c). Now these " vacuolse," whose origin and nature ap- pear to me to show their identity with the " cancelli " of bone developed from cartilage, have been described b}' L6 wig and Kolliker, and by Schacht as cells ; and the latter has even stated that they possess a nitrogenous lining membrane. This is, however, a mistake, arising from the imperfect operation of the reagents by which the cellulose is detected ; it is simply less abundant close to the cavities of the vacaolae, but may with care be demon- strated to exist up to their very edges. Botryllus, Synoicum, Syntethys, Boltenia, and the Cynthias, present a new series of ap- pearances : here the periplast of the ecderon is metamorphosed into fibres, which, however, are not composed of pure cel
Size: 1827px × 1368px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bo, booksubjectanatomy, booksubjectphysiology, booksubjectzoology
