236 THE SCOTTISH MARINE STATION AND ITS WORK. 



has already yielded fruit in the publication of several papers 

 on this interesting group of animals. 



The small crustacean Nyctiphanes norvegica is pretty com- 

 monly found in the Firth of Clyde in deep water ; when alive 

 it is a most graceful creature, swimming rapidly round the 

 aquarium, with the dorsal or ventral surface indifferently 

 uppermost. Its chief interest, however, consists in the 

 possession of luminous organs, which it shares with most, if 

 not all, the Euphausiidee. The fact that certain Schizopod 

 Crustacea have the power of emitting light appears to have 

 been first noticed by Vaughan Thompson,* and the organs 

 in question were described by Clausf under the name 

 " accessory eyes.'" The phenomenon was a matter of frequent 

 observation during the " Challenger" expedition,! and the 

 phosphorescent apparatus was described as such by Sars,§ in 

 his report on the Schizopoda, both in Euphausia and in a 

 new species of Nyctiphanes (iV. australis). He did not, 

 however, enter upon a histological examination of these 

 organs, and with a view of supplying this lacuna in our 

 knowledge Mr. Rupei't Vallentin, with the co-operation of 

 Mr. Cunningham, subjected them to a thorough investigation. 

 A large number of specimens were obtained in ninety-five 

 fathoms off Brodick Bay, and conveyed to the " Ark " at 

 Millport for examination. Each animal possesses ten of 

 these organs : one in each eye-peduncle, one in the basal 

 joint of each second and one in the basal joint of each 

 seventh thoracic appendage, while the remaining four are 

 unpaired and situated, one in the lower surface of each 

 of the first four abdominal segments. Each " photosphere " 

 (a name proposed by Messrs. Vallentin and Cunningham for 

 these structures) is a spherical body lying immediately 

 beneath the epidermis, and almost entirely independent of 

 the surrounding tissues. Its posterior half is formed by a 

 stratified, fibrous, non-cellular, hemispherical cup, within 

 which is a layer consisting of large cubical cells internally, 



* 'Zoological Researches,' ii, 1829. 



t ' Zeitschr. f. wiss. Zool.,' xiii. 



X ' Narr, Chall. Exp.' I, ii, p. 743. 



§ ' Zool. Chall. Exp.,' xxxvii, pp. 70, 119. 



