123 



absorbed the larva developes in all its organs. The pectoral fin grows into a large 

 semicircular paddle, the length increases, the black pigment of the eyes (in the 

 choroid) is developed, and the jaws acquire their definite structure. When the sole is 

 first hatched it has no mouth, and takes no food : the mouth is developed before the 

 3-olk is absorbed, but not until the absorption is completed does the young fish begin 

 to feed. The newly hatched sole is 3'55 to 3"75 mm. long, between |^th and v^ths of 

 an inch. It is perfectly symmetrical, having an eye on each side of its head, and 

 swimming vertically in the water, but it swims with its ventral edge uppermost, 

 because the yolk is lighter than the back of the fish. 



The next stage in which I have discovered the young sole is immediately after the 

 completion of its metamorphosis, that is, after it has ceased to be symmetrical and to 

 swim vertically in the water, and has taken to lying flat on the sand, and has both 

 eyes on the right side of its head. I had searched everywhere for larval soles at the 

 bottom of the sea, after the eggs had disappeared from the surface, and had had a 

 special trawl with very small meshes made to capture them with, but could not 

 discover any. At last I obtained some through the assistance of Mr. Matthias Dunn, 

 of Mevagissey, who has been for years the friend and counsellor of all naturalists 

 engaged in the study of British fishes. On April 3, Mr. l)unn sent up to the Plymouth 

 Laboratorj' a number of young living flat-fishes. I found on examination that these 

 were all Pleuronectes flesus, the flounder. Some of these were very transparent and 

 only partially metamorphosed, the left eye being still on the lower side, but near the 

 edge of the head ; in others the eye was actually in the edge of the head, looking 

 horizontally outwards. Mr. Dunn said nothing about soles, in fact at this time there 

 were no young soles in process of metamorphosis. Having failed to obtain young 

 soles by trawling, I wrote to Mr. Dunn, and arranged with him to meet him at 

 Mevagissey and examine the place where he caught his young flounders. I went to 

 Mevagissey on May 15, and found that the young flounders were found in thousands, 

 if not millions, in the pools and runlets left at low water during spring tides on the 

 bottom of the harbour. The old harbour at Mevagissey (a new additional outer 

 harbour was then being built) is completely emptied of water at the ebb during 

 springs, and the bottom consists of sandy mud. I went over the harbour with ilr. 

 Dunn, and caught numbers of the young flounders with an ordinary cup. The little 

 fish are in constant motion, some of them continually rising to the surface of the 

 shallow pools in the sand and then sinking again to the bottom. We found a few 

 soles along with the innumerable flounders. Many of the flounders were still 

 transparent and only partially or scarcely at all metamorphosed, but in all the soles 

 the metamorphosis was complete. On this day I only caught three young soles, but 

 the following day Mr. Dunn sent to me at Plymouth fifteen more. These young soles 

 were from 12 to 15 mm. long: their characters are represented in PL XVI, 3, 

 which is 83 times the natural size. They possess nearly all the characters of the 

 adult, the chief exception being that the intestine is simpler and shorter, its coils only 



