. Text-book of embryology. Embryology. 346 INVEETEBEATA CHAP. kidney which was originally the outer limb, bends inwards and fuses with the lower part of the pericardium, andliere the reno-pericardial canal is formed (Fig. 277).;. Fig. 276.—Horizontal sections tlirougli the anterior portions of three just metamorphosed specimens of Dreissensia polymorpha in order to show the transformation of the cerebral pit into the labial palps. (After Meisenheimer.) A, specimen in which the velum is just being thrown oif. B, old specimen in which the velum is already discarded, in which the cerebral pit is
. Text-book of embryology. Embryology. 346 INVEETEBEATA CHAP. kidney which was originally the outer limb, bends inwards and fuses with the lower part of the pericardium, andliere the reno-pericardial canal is formed (Fig. 277).;. Fig. 276.—Horizontal sections tlirougli the anterior portions of three just metamorphosed specimens of Dreissensia polymorpha in order to show the transformation of the cerebral pit into the labial palps. (After Meisenheimer.) A, specimen in which the velum is just being thrown oif. B, old specimen in which the velum is already discarded, in which the cerebral pit is beginning to open out. C, specimen in which the cerebral pit has given rise to two ciliated lobes, eg, cerebral ganglion ; cj), cerebral pit; , labial palps ; , mantle-cavity; oes, oesophagus; V, discarded velar cells. , The genital organ arises from a median ventral strip of the pericardial wall, in front, just between the openings of the reno- pericardial canals. It consists of peculiar large cells with pale nuclei. These cells multiply, become detached from the pericardial wall, and J J. 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-; Heape, Walter, 1855-1929. London : Macmillan
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