TADPOLES. 



103 



opens on the left side, straight backwards in Bufo, 

 backwards and upwards in the other genera (Fig. 45, 

 B, sp. ; Fig. 46, A, b). 



Pig. 46. 



Lowei' view of tadpoles of— A. Alytes ohstetricans. b. Hyla arborea. 

 (Fi-om'P. Z. S.,'1891.) 



The Lines of Muciferous Crypts or Sensory Canals. — 

 All tadpoles are provided with these organs, the homo- 

 logues of the lateral line in fishes ; they stand in imme- 

 diate relation to the nerve branches, and are regarded 

 as organs of a special sense possessed by aquatic 

 animals, feeling, in its broadest sense, having been 

 admitted as their possible use, and the function of 

 determining waves of vibration in the aqueous medium 

 having been suggested. The surface openings of these 

 tubules or canals form lines which may diflFer greatly 



