NORTH SEA INYESTIflATIONS. 15 



Billin"scrate. A statement to that effect was made at the conference of 

 the Protection Association, and I saw a considerable proportion of 

 plaice, from 5J inches upwards, among those landed at Billingsgate 

 Market on May 3rd and 4th. But I am unable to say whether any 

 were landed in London or other ports between the 9th and 24th, when 

 they were absent at Grimsby. 



III. Observations on the Natural History of Plaice. 



In order to obtain a more exact and detailed knowledge of the habits 

 and history of the fish on the North Sea fishing grounds, I have, as far 

 as time and opportunity allowed, endeavoured to ascertain the condition 

 with respect to feeding and breeding of the fish that were brought in 

 from different grounds at successive times. The observations I have 

 here to record are merely tentative and preliminary, but I think they 

 are enough to show that the method is a necessary continuation and 

 extension of those of a more general character which have already been 

 applied with good results. 



The first sample of plaice which I examined consisted of six 

 specimens caught in the north-west part of the Great Fisher Bank 

 at a depth of 35 to 39 fathoms. They were obtained in the market 

 on February 13th. There were four females 17 in. to 21 ^ in. long. 

 Three of these, 21:|^ in. to 21f in., were approaching the spawning con- 

 dition : the ovaries were much enlarged, the eggs full of yolk, but no 

 ripe eggs present: they had not commenced to spawn. In the smallest 

 female, 17 in., the roe of the right side was 3jVin. long, measuring from 

 the anterior end of the ventral fin; the end of it 6j in. from the posterior 

 end of that fin. There were no yolked eggs in the ovary. Under the 

 microscope all were transparent, but there were opaque granular masses, 

 which I believe to be evidence that spawning has taken place. I have 

 given in my paper on the " Ovaries of Fishes," in this Journal, vol. ii. 

 p. 154 to 160, some evidence that these masses are the disappearing 

 remnants of partially developed yolked ova, which are always found 

 in the spent ovary. This specimen of 17 in. would undoubtedly have 

 been considered, according to the views hitherto accepted, as immature, 

 but it seems to me it was probably a spent fish. It cannot be asserted 

 as a certainty that these granular masses never occur in an immature 

 ovary ; to settle the doubt it will be necessary to make a careful 

 examination of plaice in November and December, when all lish which 

 are about to spawn will have a large amount of yolk in the eggs, and all 

 fish in which the eggs are transparent and yolkless must be immature. 

 In other words, at that season recently-spent fish will not exist, and then 



