THE LATERAL LINE ORGANS. 37 



reckoned them all among the pit- organs. The evidence 

 for this is chiefly comparative, as the nerve supply is 

 ambiguous; see the account of their nerves in Section 7. 



The morphology and homologies of all of these pit- 

 organs are further discussed in the pages immediately 

 following and under the head of their nerves in Section 7. 



It should be noted that the "pit-organs " of Menidia are 

 not situated in pits, as in ganoids and as in the cod (Cole, 

 '98a). They are strictly naked papillae projecting above 

 the surface of the skin. Cole (p. 187 ff.) argues with 

 great force that pit-organs, visicles of Savi, ampullae and 

 lateral line canals, represent a progressively advancing 

 series in the differentiation of these organs. This seems 

 probable, and in that case the pit-organs of Menidia stand 

 nearer the primitive condition than do those of the 

 ganoids. 



1 1 1 . — C omparative. 



In all there are thirty-seven organs belonging to the 

 lateral line system proper, exclusive of pit-organs, on 

 each side of the head of Menidia. In Amia Allis' 

 enumeration shows that there are forty-seven (forty, not 

 counting those in the extra-scapular and the other more 

 posterior bones, '89, p. 499), besides the "spiracular 

 organ." To get the former number he enumerates the 

 one organ found in the supra-scapular bone and the two 

 in the supra-clavicular as belonging to the head, thus in- 

 cluding three organs behind the extra-scapular bone, while 

 I have included none behind the latter bone, since neither 

 of the other bones comes into relation with the lateral 

 line. In Gadus Cole ('98a) describes thirty-two canal 

 organs in the head. In the distribution and innervation 

 of these organs, Menidia exhibits a striking general simi- 

 larity to both of these types, though the parallelism is not 



