REPORT ON THE DEEP-SEA FISHES. 289 



2. Simple, regiilar, ocellar phosphorescent organs with pigment coat, siink in the body. 



a. Distribution. 



These organs have been found by me in Opostomias micripnus and Pachystomias 

 microdon, scattered all over tKe body at intervals of from 1 to 3 mm. In Echiostoma 

 barbatum they occur in double transverse rows on the dorSal and ventral sides of the 

 body, while in Malacosteus indicus and in Astronesthes niger they are found on the 

 ventral side only. In these species their extent is laterally limited by the lower row of 

 composite phosphorescent organs. 



Organs which belong to this group have been found by Ussow in Gonostoma 

 denudatum,^ Maurolicus amethystinopunctatus,^ and Scop)elus rissoi,^ and their position 

 corresponds, according to Ussow, with that of the composite phosphorescent organs in 

 other fishes. He seems to think that they replace the composite organs, without being 

 aware that usually (except in Sternoptyx and Argyropelecus) they are present in great 

 numbers together with the composite organs. Leydig has found such organs apparently 

 in Gonostoma denudatum, according to the figure.^ He describes them, however, as 

 having a reflector. 



Ussow considers that these organs have a glandular nature and terms them 

 " dnisenartige Organe." He considers them to be homologous to those which he 

 believes to be accessory eyes. It seems rather difficult to understand how two similar 

 and homologous organs should be so difi"erent as Ussow would make out in this case. 

 Some of the " augenahnlichen Organe " of Leydig, those namely which are not composite, 

 likewise belong to this group. 



These authors, however, have paid much less attention to these structures than to 

 the much more complicated and difierentiated composite organs, particularly those with 

 a reflector, and, consequently, the great and fundamental difi'erence between the simple 

 and composite organs has escaped their notice. Both seem to have considered the 

 presence or absence of the reflector to be of paramount importance, and did not consider 

 that some organs without reflectors were constructed on quite the same principle as others 

 which possess a reflector. 



b. Structure. 



The structure of these organs has been described by Ussow,' and his figure (pi. 

 iii. fig. 11) gives a fair representation of the internal structure. Such differences 



• M. Ussow, Ueber den Bau tier sogeuannten augeniihalichen Fleckeu einiger Knochenfische, Mim. Soc. imp. des 

 Nat. Moscou, t. liv. pp. 97, 98, pi. iii. fig. 11. 



2 M. Ussow, he. cit., p. 101, pi. iii. tig. 12. 



3 M. Ussow, loc. cit, pp. 99-100, pi. iii. fig. 13. 



* F. Leydig, Die augenahnlichen Organe der Fische, p. 15, pi. i. fig. 6. ^ M. Ussow, loc. cit 



(ZOOU CHALL. EXP. PART LVII. — 1887.) I^" "^^ 



