326 EOBEUT VALLENTIN AND J. T. CUNNINGHAM. 



swims far from the ground, while the young, up to half or 

 three quarters the size of the adult, occur abundantly at the 

 very surface, and at all intermediate depths. As mentioned 

 above, Mr. Murray found swarms of individuals at the surface 

 in the Faroe Channel, but none of these were full grown, and 

 very few more than half the adult size. Within the last two 

 or three years the species has been recognised as common 

 enough in the Clyde sea-area. 



The place where we obtained it in abundance for the 

 purpose of the examination described in this paper, was a deep 

 area ninety to ninety-five fathoms from the surface, situated off 

 Brodick Bay, and running north and south. We captured it 

 in a shrimp trawl worked from the Steam Yacht " Medusa," 

 of the Scottish Marine Station, and we took large numbers of 

 living specimens to the small house-boat laboratory called the 

 " Ark," stationed at Millport. Young specimens up to a 

 quarter of an inch long were taken by Mr. now Professor J. R. 

 Henderson in the Firth of Forth in 1884, and in June of the 

 present year we captured a number of specimens of the same 

 size at the surface by means of the tow-net, in the neighbour- 

 hood of St. Abb's Head. The eggs and larvse have never 

 been described, and, as far as we know, never captured. We 

 are unable to state whether the adult exists anywhere in the 

 Firth of Forth or its neighbourhood, or in the North Sea. As 

 the young occur at the surface in the region of the Firth of 

 Forh, it is natural to conclude that the adults occur at no 

 great distance ; but this inference requires verification. It 

 is clear that the adult is pretty widely distributed in depths 

 over, say, sixty fathoms off the north-western shores of 

 Europe. 



It is obvious from the preceding historical survey that no 

 complete histological analysis of the structure of the photo- 

 spheria in Euphausiidae has yet been made. All the organs in 

 our species, except the pair in the eye peduncles, have the same 

 structure, and fig. 1 showing a vertical transverse section of 

 the photospherion of the first abdominal segment in situ illus- 

 trates the following description : the section passes through 



