1902.] 



VARIATION IN THE NORWAY LOBSTER. 



were all obtained from the area of the Firth of Forth. In addi- 

 tion to these I procured 80 specimens which were caught off the 

 Isle of Man. Of these two were females, one was an abnormal 

 male having two pairs of genital apertures, and the rest were 



Text-fig 3. 



2 5 ^ S 6 7 e- 



Diagram illustrating variation in genital apertures in Nephrops norvegicus. 



Percentage-curve illustrating variation in the number of genital apertures in 1000 

 male specimens of Nephrons norvegicus. The lower figures give the number of 

 apertures and the side figures the percentage of individuals. 



normal males. The number is, of course, not large enough for 

 any definite conclusions to be based upon it ; but in view of the 

 fact that I never obtained even smaller batches from the Forth 

 area without finding a much higher percentage of abnormality, 

 the presence of only a single abnormal specimen among the Isle 



