i82 Journal of Comparative Neurology. 



The acustico-lateral system as a whole has been isolated 

 from the other nerve systems and plotted upon Fig, 5, the 

 canals being colored to correspond with their nerve sup- 

 ply and the limits of the related bones being indicated. 

 This plot is drawn off from the more detailed plot on Fig. 

 3 and with the exception of the naked mandibular organ, 

 man. c, and the two opercular organs, o.i. and 0.2., was 

 all drawn from a single specimen, i. e., it is not a schema- 

 tic or t3^pe sketch, but represents actual conditions, 

 individual variations not being taken into account. Com- 

 parison with many other specimens shows that such varia- 

 tions occur, but that they are of a relatively trivial 

 nature so that this outline may be taken as typical for the 

 species. 



In the more detailed plot. Fig. 3, the projection of the 

 canals and their pores is represented by the green outline. 

 The lateral line organs, like their nerves, are colored 

 brown, those organs which are contained in canals being 

 represented by brown rings, naked lateral line organs by 

 brown discs. Cutaneous organs belonging to the com- 

 munis system are represented by red discs, their nerves 

 also being colored red. 



In naming the lateral lines of the head I have used the 

 following terms : The continuation of the lateral line of 

 the trunk is termed the main line of the head up to the 

 point where it divides behind the eye. From this point 

 forward the line above the eye is called the supra-orbital, 

 the line below the eye the infra-orbital. The canal of the 

 operculo-mandibular line is interrupted between the pre- 

 opercular and the articular bones. The portion caudad of 

 this point is called the opercular line, the portion cephalad 

 the mandibular. The incomplete cross-commissure in the 

 extra-scapular bone is termed the occipital commissure. 



