TADPOLES 



i)/ 



gill-chaml ler and the iiiiuy margins of the tail: hut the change 

 from the tadpole to the final Anurous animal im])lies an almost 

 entire reorganisation. 



In the earliest condition the embryo consists of a large head 

 and body, wliile the tail is still absent. Behind the beginnings 

 of the futiu-e mouth appears a transverse crescentic fold, with the 

 convexity looking backwards, which develops into the paired or 

 unpaired adhesive (ijrp'rmf'"^- 1'liis consists of large complex 

 glands, developed in the Malpighian layer, originally covered by 

 the cuticula, which soon disappears, whereupon the sticky secre- 

 tion enables the larva to attach itself to the gelatinous mantle of 

 the egg, later on to weeds or other objects in the water. The 

 name of suckers, often applied to this apparatus, conveys a wrong 



SpT 



Fig. 9. — Four st.iges of tlie development of tlie adhesive apparatus (.1 ) of Hufo rtilijiLris .• 

 J/, Mouth ; Sp.T. spiraeular tube. In 3 the gills are almost couiph-tely hidden by 

 the united right and left opercular folds. The small outlined figures indicate the 

 shape and natural size of the tadi>oles. (After Thiele.) 



idea, there being neitlier muscles nor any suctorial function, 'i'he 

 shape of this organ undergoes many changes during the early 

 life of the individual, and ditters much in the various genera, 

 affording thereby diagnostic characters.^ .Vt first a crescent, it 

 divides into a right and a left oval or disc, which either remain 

 asunder and ))ehind the mouth {liana, Bvfo), or they move for- 

 wards to the corners of the mouth {Hyla) or further back, and 

 unite again more or less completely, as in Diseot/loss/is and 

 Boinhinator. It is mostly of short duration, and disa})pears Ijy 

 the time that the larva, by the proper development i>f tlie gills 

 and the tail and the functional mouth, changes into the tadpole. 

 But in a few species these discs transform themselves into an 

 elaborate ventral disc. Such an organ persists throughout the 

 greater part of the tadpole-stage in certain Oriental species of 

 Bana, all of wliich, when adult, possess fully webbed toes and 



' .1. Thiele, Zeit>i,-hr. irisx. ZmJ. xlvi. 18SS, ],. t57. 



