Text-book of comparative anatomy . only need to move together into the ventral middle line, so as tobecome the typical ventral chord of the Annulata. The mouth and oesophagusprevent such a moving together in the anterior part of the body, and so thefirst part of the longitudinal trunks becomes the cesophageal commissures of theAnnulata. An approximation of the longitudinal trunks, which, it is true, never leads to directcontact, may be observed as early as the Nemertina, not to speak of the as a rule among these forms the paired longitudinal trunks lie laterally,sometimes even
Text-book of comparative anatomy . only need to move together into the ventral middle line, so as tobecome the typical ventral chord of the Annulata. The mouth and oesophagusprevent such a moving together in the anterior part of the body, and so thefirst part of the longitudinal trunks becomes the cesophageal commissures of theAnnulata. An approximation of the longitudinal trunks, which, it is true, never leads to directcontact, may be observed as early as the Nemertina, not to speak of the as a rule among these forms the paired longitudinal trunks lie laterally,sometimes even over the enteric diverticula (Ampliiporus Moseleyi], they are foundin Drepanophorus placed somewhat ventrally and nearer each other. On the other IV I ERMES—NER VO US S1 K TEM 221 hand, the ventral chord of the Annelida can, by the separation of its symmetricalhalves, assume the appearance of a ladder nervous system ( in the Hrrmrllidae,Fig. 147). In very many Anmilntit (many 0/iiocJirrta and Polychceta) the brain stands in. FIG. 14(1.—Anterior part of the body of Chastogasterdiaphanus, from the side, after Vejdovsky. sb, Sensoryset<e; gz, ganglionic cells of the cup-shape1 organ; bga,ladder-like ventral chord of the pharyngeal region ; disj,, hooked setce :p, para podia ; vn, anterior pair of nc-phridia ; /in, posteriornephridia throughwliicli the sexual products are dis-charged. direct connection with the hypodermi
Size: 1518px × 1646px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booksubjectanatomycomparative
