DBVEIiOPMENT AND METAMORPHOSIS. 91 



The ceratohyal cartilage at first articulates by a 

 condyle with the suspensorium below its pr^orbital 

 process, and extends across the gular region towards its 

 fellow, from which it is separated by a narrow space, 

 with one or two small cartilaginous pieces {basihyals, 

 Parker ; copulse, Gaupp), behind which is a paired 

 plate (hyobranchials, Parker ; branchial plate, Gaupp). 

 To each branchial plate the four cartilaginous arches 

 bearing the tufted internal gills are attached by con- 

 nective tissue, and ultimately fuse with it (in the third 

 period). The homology of these branchial arches 

 has been the subject of much discussion. According 

 to Parker, they are to be regarded as subcutaneous 

 cartilages, and do not belong to the category of true 

 visceral arches ; they are called accordingly extra- 

 branchials — the true branchial arches of fishes and 

 tailed Batrachians being the ceratobranchials, repre- 

 sented by small styliform cartilages first attached to 

 the outer border of the hyobranchial cartilage, with 

 which they fuse, the fourth to persist throughout life, 

 and ossify as the thyrohijal. This view is strongly 

 refuted by the latest worker on the subject, Gaupp, 

 whose conclusions are as follows : 



The hyobranchial apparatus of the larva consists 

 of two hyalia [= ceratohyals] (Fig. 38, ch), con- 

 nected mesially by a pars reuniens ; continuous with 

 it follows the copula [basihyal, bli\, which connects 

 the hyal with the bi"anchial skeleton. The latter is 

 made up of two branchial plates [hyobranchials, hbr'] 

 and four branchialia [ceratobranchials, chr~\ on each 

 side, which pass into the branchial plates with their 

 inner extremities and into each other with their 

 dorso-lateral extremities. The whole hyobranchial 

 skeleton forms a cartilaginous continuum. For a 

 time a cartilaginous piece is developed in front of the 

 pars reuniens, which maybe regarded as a_first copula. 

 During metamorphosis the larval apparatus is for the 

 greater part lost ; the pars reuniens and the anterior 

 copula are absorbed ; the branchialia disappear with- 



