GILLS OF BATRACHIA. 



513 



341 



External gills, larva of Frog, ccxxxvm 



artery to its ventricular origin is not effected until the batrachian 

 type is passed. 



In the lower or perennibranchiate members of the order, the 

 single artery from the ventricle sends, as in Fishes, the whole of 

 the blood primarily to branchial organs, throughout life, and, in 

 all Batrachia, at the earlier aquatic period of existence ; a 

 description of the gills, permanent or deciduous, will, therefore, 

 be premised. At page 87 are described and figured, fig. 69, the 

 hyo-branchial arch and appendages of the larva of the Frog. 

 The basihyal, b, suspended by cera- 

 tohyals, a, to the tympanic pedicle, 

 e, supports a pair of cerato-branchials, 

 c, which each send off four branchial 

 arches. All these parts are cartilage. 

 The heart distributes the blood by a 

 short trunk through four pairs of vas- 

 cular arches, which, bending round 

 the gullet, reunite behind to form the 

 aorta. Before the larva quits the egg, 

 a tegumentary tubercle buds out in 

 front of the branchial cleft, and soon 

 shoots into a trifid appendage, fig. 341, 

 A and B, each process lengthening and bifurcating after the larva 

 is extricated. These filaments, of cylindrical shape, ib. c, each 

 support a single capillary 



loop, pushed out from the 312 



primitive vascular arch, and 

 are covered by ciliated epi- 

 thelium, producing the cur- 

 rents indicated by the arrows 

 in c. The branchial cavity 

 communicates at first, as in 

 Branchiostoma, with the 

 abdominal one, as well as 

 with the outer surface by 

 the branchial clefts. About 

 the fourth day these simple 

 outer gills begin to shrink ; 

 they are absorbed by the 



seventh 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 are 

 developed, at first as simple filaments, each with its capillary 



Head and branchial appendages of the larva of a Xewt 

 (Triton) niagn. CCLXVIII. 



YOL. I. 



L L 



