THE LATERAL LINE ORGANS. 43 



by nerve twigs composed in equal parts of fibres com- 

 ing from the buccalis facialis and from 'the ophthalrnicus 

 profundus. These fibres unite in a common twig that 

 goes directly to the heart of the sense organ." This ob- 

 servation is of the highest importance and should be veri- 

 fied if possible upon adult material. Without questioning 

 the accuracy of Miss Piatt's observation, a consideration 

 of her description and figures suggest certain cases which 

 I have observed in the case of Menidia, where a general 

 cutaneous twig goes out with the lateralis twig for a sense 

 organ and just before that organ is reached turns abruptly 

 to one side to supply the skin adjacent to or overlying the 

 canal organ. In an undifferentiated embryonic tissue 

 these smaller cutaneous fibres might be overlooked, or 

 they might not at the stage studied have attained their 

 ultimate growth toward the skin. 



IV. — Summary of the Lateral Lines. 



The lateral line system of Menidia is not highly devel- 

 oped, but presents very nearly the typical arrangement of 

 lines. The canal is wanting in the trunk and in a portion 

 of the infra-orbital line, though these lines are represented 

 by rows of naked lateral line organs. The organs of the 

 lateral lines, whether contained in canals or not, are 

 always innervated by the acustico-lateral system of 

 nerves. The canals are related to the bones of the head 

 in the typical manner, as described by Allis for Amia. A 

 simple pore is normally found between each pair of or- 

 gans. The lateral lines are accompanied in some cases 

 by rows of naked organs which are also innervated from 

 the acustico-lateral system of nerves and which appear to 

 correspond with the pit-lines of Amia. These pit-lines 

 are in some other fishes represented by true lateral lines. 



