370 NORTH SEA INVESTIGATIONS. 



the fish which contained such bodies had spawned, and it was 

 reasonable to suppose that those which showed no traces of retained 

 ova had either spawned a little earlier or had lost these substances 

 a little sooner than the rest. The chief question is whether the 

 fish which agreed with my ideas of immaturity might not really re- 

 present a further stage in a period of inactivity after spawning. 

 We know that when the ovary ripens for the first time its posterior 

 process forces its way backwards between the caudal muscles and 

 haemal spines towards the tail, thus attaining the elongation which 

 is familiar in the ripe condition. When the ova have been dis- 

 charged the elasticity of the ovary walls causes a considerable shrink- 

 age, apparently at once ; so that a recently spent ovary is always 

 shorter than one full of ripe ova, as well as much narrower. It 

 may be suggested that this process of shrinking is continued until 

 the ovary has reached the proportions and shape of an immature 

 example, the muscles and connective tissue also closing in on it. 

 If this were so, there could be no possible way of distinguishing the 

 spent from the immature condition apart from the presence of the 

 remains of ripe ova of a former crop. 



My evidence, however, points to the opposite conclusion, viz. that 

 the ovary, once spent, never reverts to a condition resembling that 

 of an immature fish. The fish I have referred to were nine in 

 number, and consisted of seven, diagnosed as spent, from lOf to 

 14^ inches; the three apparently immature forms measuring 11, 

 11 1, and 12 inches respectively. Now, speaking as a general rule, 

 it is the largest fish of a species which spawn the earliest ; and 

 since the ovary after spawning must needs pass through the wide- 

 walled flaccid condition, with traces of retained ova, before it could 

 reach the hypothetical stage in which it might ape the immature 

 condition, one would expect to find the latter in the largest instead 

 of, as is here the case, in nearly the smallest specimens. Eleven or 

 twelve inches is a far larger size than that at which many dabs 

 spawn for the first time ; but this is of little importance, since some 

 are quite immature up to 9 inches during the spawning season, and, 

 from the rapidity of growth which Cunningham has demonstrated 

 in the species, we can understand that a fish which fails to reach 

 the required standard, whatever it be, at the time of year favor- 

 able to the maturation of the reproductive organs, will materially 

 increase in length before the opportunity again presents itself.* 

 Apart from this I do not see how it is possible for the ovary to 

 shrink to such an extent. It would involve the atrophy of the 

 greater part of the ovarian substance, and there is no evidence 



* Probably the growth will be more rapid than in a mature fish, since there will not be 

 the same drain on the resources of nutrition for the development of the sexual products. 



