of the Fishery Board for Scotland. 



271 



VIII. — ON THE VAKIATION IN SIZE OF CERTAIN PELAGIC 

 OVA. By H. Charles Williamson, M.A., B.Sc, St Andrews 

 Marine Laboratory. 



It has been noticed that the ripe eggs of any one fish vary slightly in 

 size. In the case of certain closely allied species this variation in the 

 size of the ova makes their separation a matter of some difficulty, when, 

 as with preserved eggs, the size has chiefly to be relied upon for diagnosis. 

 The average diameter of the ova of the haddock is 1-458 mm., while 

 that of the eggs of the cod is 1*386 mm. The largest eggs of the cod, 

 however, have been found to exceed in diameter the average size of the 

 eggs of the haddock, aud at the same time the smallest eggs of the 

 haddock have been found to be almost equal to the average size of the 

 eggs of the cod. A similar relation exists between the eggs of the 

 whiting and green cod. These facts will be easily seen on reference to 

 the accompanying table, in which a comparison is instituted between the 

 sizes of the ova of several species. A detailed list of the variations in 

 size of the ova of each species which was examined is given below. 



GADID^E. 



Haddock. .,: 

 (Gadus seglefinus.) 



A collection of the eggs of the haddock were sent by Mr Dannevig 

 from Dunbar Hatchery on March 27th, 1895. They had been fertilized 

 on March 22nd. 



97 eggs were measured. 



Of these : — 



2 eggs 



measured 1*368 



mm. 



in diameter. 



1 „ 



11 



1-377 



ii 



a 



i „ 



11 



1*386 



n 



a 



s „ 



)> 



1-395 



ii 



a 



6 „ 



11 



1-404 



a 



a 



5 „ 



11 



1-413 



n 



ii 



1 » 



JJ 



1-422 



a 



a 



21 „ 



ii 



1-44 



a 



a 



2 „ 



a 



1-449 



a 



a 



7 „ 



a 



1-458 



a 



a 



6 „ 



11 



1-467 



ii 





4 „ 



II 



1-476 



a 



a 



12 „ 



11 



1-485 



a 



a 



2 „ 



II 



1-494 



a 



a 



2 „ 



>> 



1-512 



a 



a 



1 



n 



1-521 



a 



a 



1 „ 



II 



1-53 



a 



ii 



1 „ 



ii 



1-566 



ii 



a 



5 „ 



ii 



1-575 



a 



ii 



1 „ 



ii 



1-597 



a 



ii 



2 „ 



ii 



1-62 



a 



ii 



1 „ 



ii 



1-629 



ii 



ii 



1 „ 



ii 



1-638 



ii 



ii 



1 ,, 



ii 



1-665 



a 



ii 



