98 NORTH SKA INVESTIGATIONS. 



evidence of the fact in their somewhat large size, flaccid and collapsed 

 condition, and usually in the presence of a few detached ripe eggs in 

 their interior. Observers were agreed that the explanation of this fact 

 was that when spawning was finished, a certain number of eggs 

 were still only partly developed, and that these, instead of completing 

 their development, degenerated, and were gradually removed by 

 absorption in their place without being discharged. It seemed natural 

 to infer, therefore, that in every ovary in which microscopic examina- 

 tion showed the presence of these degenerating eggs, spawning 

 had previously occurred. 



This supposition has proved, however, to be incorrect. The granular 

 opaque masses have been found in the ovaries of the plaice in every 

 month of the year from February to December, and in November 

 and December have been found to occur nearly always in ovaries, 

 which showed no trace of the development of yolk in the healthy eggs, 

 which were, therefore, undoubtedly immature, the mature ovaries at this 

 time being much enlarged and far- advanced in development. At this 

 time no fish had begun to spawn, and none were in the spent condition. 

 It is clear, then, that aborted partially yolked eggs do occur in immature 

 ovaries. In different specimens these aborted eggs are seen in different 

 stages of degeneration, and it is evident that in an immature ovary 

 a small number of eggs are constantly beginning to develop yolk, 

 as though about to become ripe eggs, but almost immediately die 

 and degenerate instead of continuing their development. The same 

 process is going on in mature ovaries between the spawning seasons. 

 When the fish becomes mature, then some months before the spawning 

 season a large number of eggs continue to develop without check 

 or interruption until the crop of ripe eggs is produced. 



The plaice which, on February 27 last, I found to be mature at 

 sizes below Mr. Holt's limits, were said to have been caught off the 

 Leman Shoal, at a depth of 12 to 17 fathoms. I do not feel sure that 

 this was really their place of capture, for reasons which will appear 

 in the sequel. But I have found that the plaice, taken by the Lowestoft 

 trawlers in the neighbourhood of the Brown Badges, are certainly 

 mature at sizes similar to those which characterise the sample 

 mentioned, and considerably below Mr. Holt's limits. On October 2nd, 

 I made a complete examination at Lowestoft of a box of plaice from the 

 Brown liidges. As it was so considerable a time before the commence- 

 ment of the spawning season, I did not attempt to distinguish between 

 mature and immature males. But in many of the females yolk-forma- 

 tion had distinctly commenced, or was even somewhat advanced, and 

 these I put down as mature, the others as immature. The results are as 

 shown in the following table : — 



