202 Shelby D. Gerking 



proportionally smaller surface area and so, not only should 

 carry less surface moisture when they are weighed, but also 

 less ovarian tissue should be found surrounding the eggs in the 

 larger gonads. We can only suppose that the heavier gonads 

 produce fewer eggs per gram than do the lighter ones, so the 

 eggs are presumably larger and heavier." It is also possible 

 that the amount of connective tissue of the ovary may in- 

 crease disproportionately as it grows larger. 



After comparing the information on the haddock and long 

 rough dab, we have mixed feelings. Raitt's data were con- 

 sistent throughout and left the impression that there was a 

 slight but definite effect of age on fecundity although statis- 

 tical tests were lacking. Bagenal, on the other hand, offers 

 statistical proof to the contrary but cannot explain satis- 

 factorily at least one important feature of his data from a 

 purely biological point of view. 



Plaice. A long history is associated with studies on the 

 fecundity of the plaice. Just before the turn of the century 

 Reibisch (1899) completed a detailed study of the histology 

 of the ovary and performed many egg counts on plaice from 

 the Baltic Sea. He was acquainted with the fact that egg 

 production declines with age in higher vertebrates and was 

 puzzled to find that this was apparently not true in fishes. 

 One case was pointed out where an older and larger individual 

 produced the same number of eggs as a younger one. This 

 observation was by no means consistent, and Reibisch was 

 unable to reach a definite conclusion about the effect of age on 

 fecundity. 



Soon after, Franz (1909) duplicated Reibisch's work and 

 again was unable to answer the question. Franz admitted 

 that he had insufficient material from older age groups to 

 judge whether older plaice had a greater or lesser egg number 

 than younger ones. Individual variation was very great in the 

 specimens above age X in his sample. The lack of sufficient 

 old specimens has plagued all the studies to date and con- 

 stitutes the chief source of difficulty in settling the problem. 



