115 



if the ovary Le not mucli enlarged it usuall}' j^roduces an oi)acity extending back far 

 behind the intestines near to the base of the taih 



The enlargement of the ovaries in the female sole becomes noticeable in January and 

 February, and ripe actively moving spermatozoa ai-e found at this season by examining 

 under the microscope a portion of the testis of the male. I have not succeeded in 

 observing the natural deposition of the ova by living soles in captivity. I attempted 

 to do this in the spring of the present year (1889). At my request living soles were 

 brought to the aquarium during the previous vrinter months from the deep sea 

 trawlers and from the shrimp trawls worked in Plymouth Sound. But the specimens 

 obtained from the latter were all small, and although they lived well were too young 

 to breed ; while the larger ones from the large trawlers although living when brought 

 in invariably died after a. few days in the tanks. The reason of this was that the large 

 soles were always more or less injured by the trawl or by subsequent handling. The 

 large trawls are towed usually for a long time, six to twelve hours or more, and the 

 captured soles and other fish during this time are injured by their struggles and by the 

 pressure and weight of the whole contents of the trawl. After the soles are placed in 

 tubs of water on board the vessel the voyage back to harbour occupies a long time 

 during which they are knocked about by the motion of the vessel. In consequence of 

 this mechanical violence the skins of soles brought to me from the deep sea were 

 always more or less abraded, and the scales torn off at one or more places. The 

 injured parts of the skin in a few days always underwent inflammation and sloughing, 

 and the diseased condition spread over the surface till the fish died. I have found 

 that the sole is tenacious of life and will bear a great deal of handling so long as the 

 skin is uninjured and the scales not removed, but that very slight injury to the skin 

 and scales leads to inflammation and death. In other fish, for instance, the conger and 

 grey muUet {Mugil chelo), considerable wounds on the skin are healed up in a very 

 short time without any inflammation ; the muUet will reproduce nearly aU its scales m 

 a week or two. 



I was unable therefore to study the breeding of the sole in specimens living in 

 captivity, and my investigations of the reproduction of this species, as of many others, 

 have been carried on at sea on board of trawhng smacks by examination of the fish 

 when brought up by the trawl. 



With very few exceptions the eggs of all deep sea food-fishes have been found to be 

 small in size, spherical in shape, transparent, and buoyant in sea water, and after being 

 extruded by the parent fish to undergo development while suspended, separate and 

 independent of one another, in the surface waters of the sea. All the flat-fishes 

 investigated have been found to shed eggs of this kind, and the sole proves to agree in 

 this respect with its allies, the plaice, flounder, turbot, &c. As in other fishes, gentle 

 pressure by the fingers and thumb applied to the ovarian region of the ripe female 

 sole causes the ripe ova to escape from the aperture bj^ which the ovaries open to the 

 exterior. The ovaries lie entirely behind the aperture, and therefore the pressure must 



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