﻿130 Proceedings of the Royal Physical Society. 



one of these points in view, but as no attempt is being 

 made to establish any correlation among the different 

 features considered, the conclusions are independent of 

 the fact that different numbers were handled for each 

 investigation. 



Material. 



The material consisted partly of the stock of Norway 

 lobsters in the Zoological Department of Edinburgh 

 University, and partly of hauls taken in the Firth of Forth 

 and in the Moray Firth. Those belonging to the University, 

 which, for convenience of reference, are called " Zool. Lab." 

 specimens, were obtained from the fish-market at Newhaven, 

 and were sent in during the autumn and winter of 1906-7. 

 They were, in most cases, examined when fresh, and just 

 before being assorted and preserved for dissection. It 

 may, I think, be assumed that they were dredged in the 

 area of the Forth, from ground usually frequented by 

 Granton trawlers when fishing for Nephrops. Though the 

 quality and the numbers in the different boxfuls, which 

 were supplied at irregular intervals, varied greatly, every 

 specimen of the 1359 examples brought in was examined. 



It is desirable to give some particulars regarding the 

 others, which are divided into lots, according to place, 

 time, or method of capture. But it is necessary, in the 

 first place, to state that the ordinary trawl-net used had 

 a mesh of about 2| inches, decreasing towards the " cod- 

 end " to about If inches, and that occasionally a small- 

 mesh net, with a mesh of about half an inch, was put 

 on, as a sort of loose cover, over the "cod-end" of the 

 ordinary trawl. This small-mesh net is useful in that it 

 captures much of what might otherwise escape through 

 the wider meshes of the trawl. Some details of the various 

 hauls are summarised in Table III. The eight lots (Lots 

 A to H) represent the result of fifteen hauls. In ten of 

 these an ordinary trawl, with a head-line of 90-100 feet, 

 was used. When Lots B, C, D, and G were being caught, 

 a small-mesh net was put on in addition, and on each of 

 those occasions the numbers taken in each of the nets 



