110 INTRODUCTION. 



Millimetres. 



7. Ilijla arbor ea 50 



8. liana iberlca 50 



9. Bombinator pachypus 50 



10. liana csculenta 125 



11. ,, grseca 66 



12. ,, agilis 90 



13. ,, latastii 65 



14. ,, arvalis 75 



15. ,, temporaria 95 



16. Bufo viridis 90 



17. Dlscoglossus pictus 75 



18. Bufo calamita 80 



19. ,, vulgaris 180 



It may be noticed that the five species which head 

 the list as having proportionally the largest tadpoles 

 are the only ones in which the pupil is vertical. 



The structural differences which separate the genera 

 and species in their tadpole condition reflect, on the 

 whole, pretty accurately the system based upon the 

 perfect animals, although here and there the modifi- 

 cations are of unequal importance. We must bear in 

 mind, however, that such a correspondence, if existing 

 in the European Batrachians, is not universal. Larval 

 forms such as the tadpoles are outside the cycle of 

 recapitulation, the ontogeny being broken by the 

 intercalation of the larval phasis. The horny beak, 

 the circular lip with its horny armature, the spi- 

 raculum, the enclosure of the fore limbs in diverticula 

 of the branchial chambers, and such special adapta- 

 tions as the ventral disk or sucker of certain exotic 

 mountain forms, clearly point to tadpoles having 

 had a developmental history of their own. We need, 

 therefore, not be surprised at occasionally finding, 

 within the same genus, very different types of tad- 

 poles, or even a total suppression of the free larval 

 stages, as is actually the case in the large and widely 

 distributed genus Bana. 



