154 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



(1.) Anterior region, 10 grains contained ... 744 ova. 



„ „ „ ••• 762 „ 



Middle region, „ „ „ ... 721 ,, 



„ „ ... T30 „ 



Posterior region, ,, ,, „ ... 701 ,, 



,, ,, „ >, ?? ■•• 735 ,, 



Average for 10 grains = 732 ova. 



(2.) Anterior ventral region, 10 grains contained 804 ova. 



„ „ „ „ 789 „ 



Anterior ventral lobe, ,, „ ,, 853 ,, 



„ 870 „ 



Middle region, ... „ ,, „ 810 ,, 



• •• „ „ „ 857 „ 



Posterior region, ... „ ,, „ 886 „ 



Average for 10 grains = 838 ova. 



The differences in number of the ova in the various 

 samples were due chiefly to the mixture in various pro- 

 portions of eggs of slightly different size, and also to the 

 varying admixture of water and connective tissue — both 

 sources of error which are unavoidable in this method of 

 investigation. Two kinds of ova are present in the roe of 

 the plaice, (1) large ova lightly attached or lying freely 

 in the lumen of the ovary, and smaller immature ova still 

 adherent to the epithelium. In fish (2) which had not 

 begun to spawn, I counted 492 large mature ova in one 

 ovary; their diameter was 1'32 mm. Nearly all the 

 remaining ova were about 1 mm. in diameter, and there 

 were few intermediate in size. This is in accord with the 

 general belief that the process of ripening, or the absorp- 

 tion of fluid by the ova, is very rapid. Fish (1) had just 

 begun to spawn, but a similar contrast between mature 

 and immature ova was evident. 



