. Text-book of embryology. Embryology. 384 INVEKTEBEATA CHAP. If Caldwell has given the details of the metamorphosis correctly it is exceedingly difiicult to interpret, for his account would seem to imply that the apical plate and subjacent ganglion are sacrificed, in which case the cerebral ganglion of the adult must be a new aten. Fk!. 311,âTliree stages in the meta- morphosis of the Actinotrocha larva of Phoronis, seen from the side. (After Metschnikoff.) A, Bt:iK<^ in â which the vential pcto- (Inrmic invagination has just made its appearance. B, stage in which the ventral iiiva^nnation
. Text-book of embryology. Embryology. 384 INVEKTEBEATA CHAP. If Caldwell has given the details of the metamorphosis correctly it is exceedingly difiicult to interpret, for his account would seem to imply that the apical plate and subjacent ganglion are sacrificed, in which case the cerebral ganglion of the adult must be a new aten. Fk!. 311,âTliree stages in the meta- morphosis of the Actinotrocha larva of Phoronis, seen from the side. (After Metschnikoff.) A, Bt:iK<^ in â which the vential pcto- (Inrmic invagination has just made its appearance. B, stage in which the ventral iiiva^nnation is partly everted. C, stage ill which the nietaniorphc'^is is almost complete. , rudiments of adult tentacles; gl^ glandular pocket of the stomach regard ed by Mastertnan as a homologue of the notochord ; int, intes- tine; inv, ectodermic invagination which becomes everted to form the body of the worm ; , larval tentacles of the metatroch; , prae-oral lobe; st, stomach ; , telotroch. formation. Now in the metamorphosis of every Trochophore so far studied, the apical plate and the associated ganglion form the head- blastema, and persist through larval life into the adult condition. It is possible that Caldwell has made a mistake in this matter, and that it is the hood in front of the ganglion, which we have already compared to a broad prototroch bearing minute cilia, which is. 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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