. The elasmobranch fishes . Fig. 165 Fig. 164 Fig. 164. Arteries derivative of the first efferent-collector, Squahis suoldii. (L. H. Bennett, orig.) }, first branchial efferent; , external carotid; }--, first and second efferent- collector arteries; , hyoidean efferent; ps., pseudobranchial artery. Fig. 165. Cross-trunks from eighth to ninth efferent-collectors, Squalus sucklii. (L. H. Ben- nett, orig.) ct., cross-trunk; }'^, eighth and ninth efferent-collectors. tain a dorsal commissural connection with the anterior efferent-collector of the same gill. This interesting c
. The elasmobranch fishes . Fig. 165 Fig. 164 Fig. 164. Arteries derivative of the first efferent-collector, Squahis suoldii. (L. H. Bennett, orig.) }, first branchial efferent; , external carotid; }--, first and second efferent- collector arteries; , hyoidean efferent; ps., pseudobranchial artery. Fig. 165. Cross-trunks from eighth to ninth efferent-collectors, Squalus sucklii. (L. H. Ben- nett, orig.) ct., cross-trunk; }'^, eighth and ninth efferent-collectors. tain a dorsal commissural connection with the anterior efferent-collector of the same gill. This interesting condition obtains in the adult Chlamydoselachus (fig. 160). In this form the posterior efferent-collector sends a branch to join the efferent-collector back of it, but it also retains an embryonic attachment with the anterior efferent of its own holobranch. Usually, however, the branch connecting it to the succeeding efferent-collector becomes so important that the original connection of the posterior efferent-collector to its own efferent anteriorly is entirely lost in the adult. In any event there results in the adult a complete efferent circuit around the gill cleft, each circle being composed of the posterior efferent-collector of one gill and the anterior efferent-collector of the gill following. Around all the clefts (except the last) and the spiracle, complete loops are formed as thus described. Since there are no demibranchs posterior to the last cleft no efferent-col- lector lies back of this cleft and hence a circuit is incomplete around it. The last posterior efferent-collector, that one in front of the last cleft, is usually
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