. Text-book of embryology. Embryology. XVI ECHINODEEMATA 465 dorsal arms (jiAm, Fig. 358). Where the sides of the post-oral band pass into the anal loop two long arms are developed, termed the postero-lateral arms {, Fig. 358). Finally, from the sides of the anal loop two short arms are developed, termed the post-oral arms (^, Fig. 358). The two coelomic sacs are, for a considerable time, two somewhat rounded pockets lying at the sides of the oesophagus. The one on. a:Ci mt Fig. 368.—Fully developed Bipiuuaria larva of Asterias vulgaris, atout three weeks old. (After Field.) A, from
. Text-book of embryology. Embryology. XVI ECHINODEEMATA 465 dorsal arms (jiAm, Fig. 358). Where the sides of the post-oral band pass into the anal loop two long arms are developed, termed the postero-lateral arms {, Fig. 358). Finally, from the sides of the anal loop two short arms are developed, termed the post-oral arms (^, Fig. 358). The two coelomic sacs are, for a considerable time, two somewhat rounded pockets lying at the sides of the oesophagus. The one on. a:Ci mt Fig. 368.—Fully developed Bipiuuaria larva of Asterias vulgaris, atout three weeks old. (After Field.) A, from the ventral surface. B, from the surface, a, anus ; , anterior dorsal arm; , adoral ciliated band ; fus, anterior fusion of right and left coelomic sac; int, intestine ; , left coelomic sac; , median dorsal arm; , madreporic pore ; oes, oesophagus ; , postero-dorsal arm; , postero-lateral arm ; , post-oral arm ; , post-oral band of cilia; , prae-oral arm ; , prae-oral band of cilia ; , right coelomic sac ; at, stomach ; stom, stomodaeum. the left side sends up a short vertical outgrowth which fuses with a slight inward dip of the ectoderm, and in this way forms a canal leading to the exterior. The opening of this canal is termed the primary madreporic pore (m-p, Fig. 359), and the canal itself is termed the pore-canal. Its wall is covered with cilia which beat inwards and strive to distend the coelomic sac with sea-water. Twenty years ago Field (1894) stated that, in the case of Asterias vulgaris, the right coelomic sac formed a similar pore-canal, terminat- ing in a right madreporic pore (m^^i. Fig. 359), which soon, how- VOL. I 2 H. 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 MacBride, E. W. (Ernest William), 1866-1940; Kerr, John G
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Keywords: ., bookcentury1900, bookdecade1910, bookpubli, booksubjectembryology
