117 



and consequently higher temperature of the sea in the spring of 1889. In the latter 

 year, when on board a trawler south of the Wolf Eock which lies to the west of the 

 Land's End, on April 11 and 12 I found nearly all the female soles completely 

 spent, a few containing nothing but a small number of ripe ova. The surface tempera- 

 ture of the sea at that time and place was 48'5 F. (9 0- 2 C.). In 1888 the fisherman in 

 the service of the Plymouth Laboratory obtained ripe soles on April 26 and 27 at a 

 distance of 40 miles north of the Land's End where the surface temperature was 46 0> F. 

 (7-7 C.) and the bottom temperature at 50 fins, was 45'0 F. (7-2 C.). The temperature 

 on April 6, 1888, to the south of the Wolf Eock was 46'0 F. (7-7 C.). The following 

 temperatures of the surface of the sea will show the difference of the two seasons : 



I have not determined so exactly the commencement of the spawning period in the 

 two seasons. In 1888 I examined several soles taken nine or ten miles W. by S. 

 of the Eddystone, on February 6. Only one yielded a few ripe ova, about a dozen ; 

 the rest were all unripe. 



It is thus evident that the spawning period of the sole extends from the middle of 

 February to the end of April ; but that the greater number of individuals shed their 

 spawn in March, and the early part of April ; and that in warm seasons the spawning 

 is completed by the end of the second week in April ; while in colder seasons some 

 individuals are found still spawning up till the end of April, and a few eggs may not 

 be shed till the middle of May. 



Little has yet been said about the males. Necessarily the male reproductive 

 elements consisting of the fluid milt, which contains the innumerable spermatozoa, 

 are discharged at the same period as the ova. But the testes and the milt of the sole 

 differ remarkably from those of any other marine fish I have examined. In other 

 fishes the testes in the spawning season are much enlarged, and very soft, so that 

 when the fish is opened very slight handling tears or ruptures the testes, causing the 

 escape of a thick viscous opaque white fluid, the milt. When the ripe male fish is 

 gently squeezed the milt escapes from the genital aperture in large white drops 

 having the appearance of milk, which when allowed to fall in sea water mix with it 

 and render it turbid. But when a male sole is opened in the breeding season the testes 



