APPENDIX A. 



REPORT on the Structure of the Peculiar Organs on the Head of Ipnops. By 

 Professor H. N. Moseley, F.R.S. (Pis. LXVIL, LXVIIL). 



In the General Report on the Scientific Results of the Voyage of H.M.S. Challenger,^ 

 some account is given of the structure of the peculiar organs existing on the head 

 of Ipnops murrayi. As there stated, Mr. John Murray was the first to examine these 

 organs by means of sections, and point out their remarkable peculiarities. He concluded 

 that the organs were organs of luminosity, and Dr. Giinther formed the same opinion 

 from his examinations of the specimens. Mr. Murray kindly placed his sections at my 

 disposal ; they did not show any structure very clearly, and being misled by an unlabelled 

 slide placed with the rest and containing a section of the retina of some ordinary 

 teleostean fish, and which I attributed to Ipnops, I formed the opinion that the 

 peculiar organs of that fish were essentially retinal in structure, and hence arrived at the 

 conclusion that the organs must be regarded as modified organs of vision. 



Mr. Murray's preparations not being sufficient for any definite conclusions as to the 

 structure and relations of the peculiar organs, Dr. Giinther kindly placed a perfect 

 specimen of Ipnops at my disposal for a detailed examination, and on making a complete 

 series of sections of the head I found no trace of any retina-like organ and soon realised 

 my mistake. The peculiar organs have in reality no connection with organs of vision. 

 The eyes, as well as the optic nerves, are entirely aborted in the fish, and the organs 

 are apparently not sensory at all, but most probably phosphorescent, as Dr. Giinther 

 and Mr. Murray at first concluded. I have to express my thanks to Sir Henry Aclaud, 

 K.C.B., Librarian of the Radcliffe Library, for permitting me to publish the drawing 

 reproduced on PI. LXVIL by the artist of the Library. 



I shall term the organs the phosphorescent organs, for the purposes of description here. 

 The organs are paired expanses completely symmetrical in outline, placed on either 

 side of the median line of the upper flattened surface of the head of the fish, and ex- 

 tending from a line a little posterior to the nasal capsules nearly to a point above the 

 posterior extremity of the cranial cavity. They are covered by the upper wall of the 



1 Narr. Cliall. Exp., vol. i., part i., p. 239. 



