The Photospheria of Nyctiphanes Norvegica, 

 G. O. Sars. 



By 



Rupert Valient in 



and 



•J. T. Cunningham, B.A., 



Fellow of University College, Oxford. 



With Plate XXIII. 



It has long been a familiar fact to zoologists that in nearly 

 all the Schizopodous genera which form the family Euphaus- 

 iidae are present ten small globular, reddish organs, having a 

 resemblance in many respects to such eyes as those of Verte- 

 brata and some Mollusca and Cluetopoda. The organs in 

 question have not the least resemblance to the typical com- 

 pound eye which is so characteristic of Arthropoda, but 

 because when one of them is examined in the fresh state, a 

 doubly convex structureless lens, and a cell layer suggesting 

 the idea of a retina, are easily seen, therefore the organs were, 

 until a recent date, generally denominated accessory eyes, or in 

 German " Nebenaugen." 



One of the earlier descriptions of the organs is in a paper 

 by Claus 1 published in I860. He says there that one of the 

 conspicuous characters of Euphausia is the presence of acces- 

 sory eyes, some of which are median unpaired, some lateral 

 and paired. In proceeding to give an account of the structure 



1 " Ueber einige Schizopoden und niedere Malacostraken Messina's," 

 ' Zeit. f. wiss. Zool.,' Bd. xiii, 1S63. 



VOL. XXVIII, PART 3. NEW SER. Z 



