GILLS OF BATRACIIIA. 



313 



341 



artery to its ventricular origin is not effected until the batracliian 

 type is passed. 



In the lower or percnnibranchiate members of the order, the 

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

 the Ijlood jn-imarily to branchial organs, throughout life, and, in 

 all Batradiia, at the eaidier 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 Fmg. 

 The basihyal, h, suspended l)y cera- 

 tohj'als, a, to the tympanic pedicle, 

 e, supports a pair of cerato-branohials, 

 c, which each send off four branchial 

 arches. All these parts are cartilao-e. 

 The heart distributes the blood by a 

 short trunk througli four pairs of vas- 

 cular arches, wliich, bending round 

 the gullet, reunite behind to form the 

 aorta. Before the larva quits the egg, 

 a tegumentary tubercle buds OTit in 

 front of the branchial cleft, and soon 

 shoots into a trifid appendage, fig. 341, 

 A and B, each process lengthening and 

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

 suj^port a single cajiillary 



loop, pushed out from the S'i2 



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 

 Br and do stoma, 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 



VOL. I. L L 



Ifurcating after the lar 



•va 



Head ami bvancliial aiipeiidagcs of the larvaof a Newt 

 iTritoJi) magn. ccLxviir. 



