670 GREENE. [Vol. XV. 



The lateral-line organs are located free on the surface with 

 the exception of certain rows on the head which are in canals. 

 These lines of canal organs form only a small part of the lateral- 

 line system in Porichthys. Unless otherwise specified, surface 

 organs are meant. 



It is impossible to determine the homologies of the parts of 

 the complex lateral-line system without a knowledge of the 

 development of the sensory Anlage and of the innervation of 

 the system, including the origin of the nerves in the central 

 nervous system. Such a study has been made in part for only 

 a few fishes, while the great mass of fishes remain unknown 

 in this regard. It is necessary, therefore, while awaiting the 

 development of our knowledge of the origin and distribution of 

 the lateral-line nerves, to designate the groups of lateral-line 

 organs in particular species by some sort of descriptive terms. 

 The intention in this paper is not so much to name the groups 

 in Porichthys as to describe their location by short descriptive 

 terms that will serve temporarily, i.e., until we have a surer 

 foundation for establishing homologies between the parts of 

 the lateral-line system in different species of fishes, when a 

 permanent nomenclature may be adopted. 



I. Lines of Organs on the Body. 



The lateral row, la (PI. XXXVIII, Figs. 1-3), begins 

 on the side at a point posterior to the upper border of the 

 pectoral fin and directly below the third dorsal ray. It runs 

 straight back along the side to the upper third of the base of the 

 caudal, and contains both kinds of organs. This line contains 

 an average of thirty-six sense organs with a phosphorescent 

 organ immediately below and generally one above each sense 

 organ. In the lower series the phosphorescent organs are well 

 developed and large, but the organs of the upper series are 

 quite small and rudimentary ; in fact they are often wanting, 

 there being only an average of twenty-two in the fifteen speci- 

 mens tabulated. The organs in this line correspond very nearly 

 with the segments of the part of the body along which they lie. 

 They are found above the grooves which mark the boundary 

 between the myomeres. 



