No. 3] PHOSPHORESCENT ORGANS. 67 1 



The "pleural" row, //, consists of parallel lines of phos- 

 phorescent organs and sense organs. The row of phosphores- 

 cent organs begins at a point posterior to the middle of the 

 base of the pectoral and below the anterior ray of the dorsal 

 fin. The line curves backward and downward to a point back 

 of the lower edge of the pectoral and above the first anal ray, 

 thence straight back along the side, ending usually above the 

 twenty-third anal ray. The organs of this line vary in number 

 from forty-three to sixty-two, or an average of fifty-three, and 

 have no relation to the body segments. The row of sense 

 organs is located immediately below the row of phosphorescent 

 organs and follows the same general course. This row usually 

 extends backward only to the thirteenth anal ray, but in three 

 specimens from Alaska (see Table, Nos. 8-10) the row extends 

 to the base of the caudal fin. There is an average of thirty- 

 two sense organs in the row, excluding the three exceptions 

 mentioned. In these three there are sixty, bringing the general 

 average up to thirty-six. 



There are two caudal, ca, lines of sense organs on each side 

 the fin, located on the upper and lower thirds, respectively. 

 These rows contain only sense organs, which are well devel- 

 oped at the base of the caudal, but become smaller toward the 

 extremity of the fin. There are as many as twenty-five in each 

 line in the oldest specimens, but the number varies greatly, 

 increasing with the age of the specimen. These rows are in 

 line with the lateral and pleural rows of sense organs, but they 

 are not continuous with them. 



The "anal" row, a, runs along the body on either side of 

 the base of the anal fin from opposite the interspace between 

 the second and third anal rays to the base of the caudal. The 

 phosphorescent organs of this line correspond in position to 

 the anal rays and are in pairs, with exceptions to be mentioned. 

 The first organ is usually single ; the next twenty-eight or 

 twenty-nine, paired ; the last six or seven, single. The last 

 four or five organs are situated under the base of the caudal 

 and are arranged in a markedly compact row. There is an 

 average of thirty-six organs in this row, counting the pairs but 

 once. The outer organs of the pairs are apparently larger than 



