48 THE PHOSPHORESCENT ORGANS 



but little, and some none. But the amount of pigment, and 

 indeed the development of the organs, varies in the differ- 

 ent specimens of the fish examined. In some specimens, 

 the organs, especially on the ventral surface, were plainly 

 not much changed from their original state of slime glands. 

 In the specimen in which the organs were best developed, 

 there were present not only all the organs figured in my 

 plate, but there were additional rows of slime glands (or 

 mucous pores) changing into phosphorescent organs. This 

 was particularly noticeable, first, on the ventral surface ; 

 second, in a row of slime glands which had appeared just 

 below the pleural row, and running along with it, a slime 

 gland for each phosphorescent organ; third, in the central 

 slime gland row of the lateral row, where the slime glands 

 were changed into phosphorescent organs ; and, fourth, in 

 the organs of the mandibular row, which though in some 

 specimens only slime glands, in this fish possessed lenses, 

 reflectors, and a little pigment. 



Indeed, even by examining the small series of speci- 

 mens of Porichthys contained in the Museum of Indiana 

 University, some twenty fish in all, the evolution of the 

 phosphorescent organs from slime glands is apparent. 



In order that the various points of the organs of the dif- 

 ferent rows may be described and understood , I will des- 

 ignate the "ends" of the organs as anterior and posterior, 

 according to the end of the fish they are nearest. Like- 

 wise the "sides" are called dorsal and ventral from their 

 respective proximity to those surfaces of the fish. 



Series of sections of the following rows were cut : outer 

 anal, frontal, upper opercular, gastric, pleural, lateral and 

 ventral. 



The outer anal organs (fig. 7) are, from a surface view, 

 almost exactly circular. The broad spicular layer is thick- 

 est, and slightly turned up at the edges. Thus, it is 



