444 Mr Mcintosh, On Variation in the Norway Lobster. 



It is well known that Norway lobsters are gregarious, but 

 my observations do not indicate that they are found in shoals 

 according to sex. 



In all investigations bearing on this point it is absolutely 

 essential for each investigator to superintend the operation of 

 dredging. It seems useless to draw conclusions as to relative 

 frequency of sex from specimens provided by fishermen in the 

 ordinary course of their calling, for it may very w r ell be that they 

 allow the smaller individuals to escape. It is well known that 

 they do not expose for sale (since to do so is contrary to law) 

 the female crab {Cancer pagurus) carrying ova, and it may be 

 that they also allow the female Norway lobster, if carrying ova, 

 to escape. In this connection I found that 10'2 per cent, of the 

 Clyde female lobsters were laden with ova, and one could not 

 examine many of these without remarking on the comparatively 

 small size of mature females. 



From the facts recorded in Table III it may probably be 

 concluded that for the Clyde area (1) the proportions of the sexes 

 in Nephrops norvegicus are approximately equal, and (2) the size 

 of fully grown males is considerably greater than that of fully 

 grown females. This would be in agreement with Punnett's 

 conclusions 1 as to the relative frequency and relative size of the 

 sexes in Carcinus maenas. Table III also illustrates the possi- 

 bility of error in drawing any conclusion as to the relative 

 frequency of males and females from an examination of specimens 

 at any particular stage of growth. 



It may be added as an interesting fact that the Norway 

 lobsters of the Clyde were invariably found associated with those 

 of their own size. One haul, for example, would contain only 

 large specimens, another only medium sized, while a third con- 

 tained only specimens of small size. I hope to refer more fully to 

 this and other points in a future paper. 



In conclusion, my hearty thanks are due to the officials of the 

 West of Scotland Marine Biological Association (and especially 

 to Mr Gray, lately Curator of the Marine Station at Millport) for 

 their kindness in allowing me the use of the S. Y. "Mermaid" to 

 procure the specimens used in this investigation, and to Professor 

 J. Arthur Thomson for permission to occupy the " Aberdeen 

 University Table." 



1 Proc. Camb. Phil. Soc. Vol. xn. 1903. 



