Ig4 VERTEBRATE ZOOLOGY 



10. Lateral line sense organs are present at least during the larval 



stage. 



11. The vagus is the last cranial nerve. 



12. The median fins, where present, are not supported by spinal 



skeletal rays. 



13. Sternal ribs and a costal or true sternum are absent. 



14. There is no paired or unpaired medio-ventral copulatory ap- 



paratus. 



15. Development takes place without amnion and allantois. 

 None of these characters is absolutely diagnostic, except 1 (c), and 



this applies only to Anura and most of the Stegocephali. 



Numbers 1 (b), 1 (c), 2, 3, 4, and 12 separate the Amphibia 

 from the Fishes. 



Numbers 1, 6 (b), 7, 8, 9, 11, 13, 15, separate them from the Rep- 

 tUes, Birds, and Mammals. 



Niunber 2 separates them from Fishes, Reptiles, and Birds. 



Number 6 (a) separates them from the Fishes (excl. Dipnoi), 

 Birds, and Mammals. 



Gadow says: " AmpUcondylcms Anamnia would be an absolutely 

 correct and all-sufiicient diagnosis" of Amphiba, but concludes that 

 "Amphicondylous anunals without an intra-cranial hypoglossal 

 nerve," is a more practical diagnosis. 



Order I. Apoda (Gymnophiona) — Limbless Amphibia 



The Apoda or caecilians, sometimes caUed "blind worms," consti- 

 tute a small group of about forty species, living in the warmer parts 

 of the world, but widely distributed. They are worm-shaped, bur- 

 rowing creatures (Fig. 108, A) with habits somewhat like those of 

 earthworms and not unhke them in appearance. They have no limbs 

 nor Kmb-girdles and there is also the merest rudiment of a tail; hence 

 the anal opening appears to be terminal. The skin is folded into nu- 

 merous ring-like folds and is smooth and slimy. Small deep-set der- 

 mal scales occur, which are believed to be an inheritance from stego- 

 cephalian ancestors. The cranium is very solid and compact in 

 appearance, more like that of a reptile than that of other modern Am- 

 phibia, but the same bones as in other Amphibia are present in a 

 broadened-out form. The vertebrae are pseudocentrous and extremely 

 numerous, being as many as 200 to 300 in some species. The eyes 

 are rudimentary and practically functionless. They feel their way 



