THE VISCERAL AFFERENT DIVISION. 165 



(2) In ganoids and bony fishes (Amia, Catostomus} they arise in 

 the entodermal lining of the pharynx, oesophagus and mouth. 

 After the time of hatching, the mucosa pushes out over the lips 

 and taste organs appear in the spreading entoderm. (3) In am- 

 phibians (Amblystoma punclatum, Rana) the taste buds arise and 

 remain throughout life in the entodermal area of the pharynx and 

 mouth. Although the limits of ectoderm and entoderm have not 

 been determined in reptiles, birds and mammals, the most rea- 



15 



FIG. 85. Sense organs of bony fishes. A, a taste bud from the oesophagus of 

 Catostomus at the time of hatching; B, a taste bud from the pharynx of the same 

 embryo; C, two neuromasts from the skin of the same embryo. 



sonable inference from the position of the organs is that they lie 

 in entodermal territory. 



The taste organs differ from the pit and canal organs: (i) in 

 being surface organs not sunken in pits but sometimes projecting 

 above the surface as hillocks; and (2) in that the sense cells are 

 long, slender and rod-shaped and extend the full depth of the 



