76 
latter method a certain amount of ovarian tissue is 
estimated as ova, and a number of very small ova which 
will not be spawned at the next spawning period are also 
included. — In two of Reibisch’s estimations the weight 
of the ovaries after complete spawning was 7°8 grms. and 
185 grms. By employing this method Reibisch made a 
large number of estimations, some of which are quoted 
in the following table :—- 
Total length in | Total weight in ‘Total number of ova 
Cms. | Gims. in the fish. 
; | | 
1 54 lo “e770 223,250 
2 45 969 109,500 
3 42 1,100 | 558,500 
4 | 40°5 | 698 | 736,250 
a | 38°5 585 250,750 
| 
Reibisch did not count the very small eggs which are 
always present in the ovary. If these had been included 
values of 24 millions of ova would have been obtained in 
some cases, and this represents a degree of fecundity 
certainly not attained by the plaice. Such very small 
egos he contends cannot ripen for the next spawning period. 
All these results, and my own have the same tendency, 
show, as Keibisch has observed, that there is no recog- 
nisable relationship between the size or weight of the fish 
and the number of eggs produced by it at the spawning 
period. The age of the fish has in all cases to be consi- 
dered. We know that the rate of growth is very variable. 
Probably most plaice attain sexual maturity at the same 
age, but the size and weight at this age may be very 
different in a number of specimens. Thus a mature 
female 13 inches long, and an immature female of 19 
inches, have been taken from the Irish Sea. 
