. Text-book of embryology. Embryology. 532 INVEETEBKATA CHAP. into oesophagus, stomach, and intestine. This last division is bent forwards, so that, as in other Echinoderm larvae, the alimentary canal is bent in a curve, concave ventrally. The stomodaeum is formed in the usual manner on the ventral side of the larva; it joins the oesophagus after the coelom has been separated from the alimentary canal. The general covering of cilia becomes lost as the ectoderm cells flatten out, and the cilia become restricted to ridges which form a. coe Fig. 396.—Two young larvae of Synapta digituta viewed fr
. Text-book of embryology. Embryology. 532 INVEETEBKATA CHAP. into oesophagus, stomach, and intestine. This last division is bent forwards, so that, as in other Echinoderm larvae, the alimentary canal is bent in a curve, concave ventrally. The stomodaeum is formed in the usual manner on the ventral side of the larva; it joins the oesophagus after the coelom has been separated from the alimentary canal. The general covering of cilia becomes lost as the ectoderm cells flatten out, and the cilia become restricted to ridges which form a. coe Fig. 396.—Two young larvae of Synapta digituta viewed from the side. (After Selenlca.) A, formation of the coelom. The coelomic part of the archenteron opens to the exterior by the madre- poric pore before it is separated from the gut-portion of the archenteron. B, formation of the mouth and stomodaeum. al, alimentary canal; ap, apical thickening ; hip, blastopore; coe, coelomic vesicle; mp, madreporic pore; stom, stomodaeum. folded longitudinal band. This band resembles that of the Bipinnaria larva of Asteroidea in its earlier stages of development, it consists of right and left longitudinal pieces and anterior and posterior cross- bars, the former of which is bent backwards over the prae-oral region of the larva as the prae-oral loop, and the latter of which is bent forwards in front of the anus as the anal loop. An adoral band of cilia is formed in the same way as has been described for the Bipinnaria, Ophiopluteus, and Echinopluteus. The Holothuroid larva differs from the Bipinnaria in two points: first, the prae-oral loop, although almost, is never quite constricted from the rest of the band, so that the longitudinal band of cilia. 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 Graham, 1869-; He
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