. Outlines of zoology. Zoology. COMPLICATED FORMS OF SPONGES. 119 sheath of —subdermal. Fig. 33.—Diagram showing types of Canal System. (After and Heider.) The flagellate regions are (lark throughout, the mesoglcea is dot- ted, the arrows show the direction of the currents. All the figures represent cross sections through the wall. A. Simple Ascon type, Ec. ectoderm, Efi. endoderm, .1/^. mesoglcea. B. Sycoft type, with tlagellate radial chambers i^'). C. Lencon type, with flagellate side aisles on the main radial chambers. D. Still more complex type, with small flage
. Outlines of zoology. Zoology. COMPLICATED FORMS OF SPONGES. 119 sheath of —subdermal. Fig. 33.—Diagram showing types of Canal System. (After and Heider.) The flagellate regions are (lark throughout, the mesoglcea is dot- ted, the arrows show the direction of the currents. All the figures represent cross sections through the wall. A. Simple Ascon type, Ec. ectoderm, Efi. endoderm, .1/^. mesoglcea. B. Sycoft type, with tlagellate radial chambers i^'). C. Lencon type, with flagellate side aisles on the main radial chambers. D. Still more complex type, with small flagellate chambers,_/; ch. chambers, by flat epithelium with spaces may be formed ; an outer cortex may be distinctly differentiated from the internal region in which the flagellate chaiTibers occur ; the pores may collect into sieve-like areas which open into dome - like cavities; these and many other complications are common. {d) The ectoderm is usually described as a covering layer of flat epithelium, but flask shaped cells have also been observed (Bidder). It may be folded in- wards, as we have noticed, and, according to some, it also lines the incurrent or afferent canals in whole or in part. In a few cases, , Oscarella lobularis, it is ciliated, and its cells may also exhibit con- tractility, as around the osculum of Ascetta cla- thriis, though the con- tractile elements usu- ally belong to the meso- glcea. The endoderm con- sists typically of collared flagellate cells, but in the more complex sponges these are replaced, ex- cept in the flagellate or without 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 Thomson, J. Arthur (John Arthur), 1861-1933; Newbigin, Marion I. (Marion Isabel), 1869-1934; Smith, Preserved, 1880-1941. fmo. New York, D. Appleton & Co.
Size: 1115px × 2242px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
