. On the anatomy of vertebrates [electronic resource] . ches, which, bending roundthe gullet, reunite behind to form theaorta. Before the larva quits the egg,a tegumentary tubercle buds out infront of the branchial cleft, and soonshoots into a trifid appendage, fig. 341,A and B, each process lengthening and bifurcating after the larvais extricated. These filaments, of cylindrical shape, ib. c, eachsupport a single capillary loop, pushed out from the 342primitive vascular arch, andare covered by ciliated epi-thelium, producing the cur-rents indicated by the arrowsin c. The branchial cavitycommu
. On the anatomy of vertebrates [electronic resource] . ches, which, bending roundthe gullet, reunite behind to form theaorta. Before the larva quits the egg,a tegumentary tubercle buds out infront of the branchial cleft, and soonshoots into a trifid appendage, fig. 341,A and B, each process lengthening and bifurcating after the larvais extricated. These filaments, of cylindrical shape, ib. c, eachsupport a single capillary loop, pushed out from the 342primitive vascular arch, andare covered by ciliated epi-thelium, producing the cur-rents indicated by the arrowsin c. The branchial cavitycommunicates at first, as inBranchiostoma, with theabdominal one, as well aswith the outer surface bythe branchial clefts. Aboutthe fourth day these simpleouter gills begin to shrink;they are absorbed by theseventh day. The cartilaginous arches, also beginning to shrink,become more internal by the progressive growth of the head. In the Newt {Triton, fig. 342), three pairs of external gills aredeveloped, at first as simple filaments, each with its capillary. Head and branchial appendages of the larva of a Newt(Triton) niagn. cclxviii. VOL. I. L L 514 ANATOMY OF VERTEBRATES. 343 loop, but speedily expanding, lengthening and branching intolateral processes with corresponding looplets ; these blood-channelsintercommunicating by a capillary network, as at d, fig. 343. The gill is covered by ciliatedscales, ib. e, which changeinto nonciliated epithe-lium, f, shortly before thegills are absorbed. The size of the mils is asthe proximity of their deve-loping vascular arch to thepropelling organ of theblood. In the Proteusanguinus three pairs onlyarches are developed, correspondinggills. In Siren lacertina, as inbranchial
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