131 



ripe males of other fislies I liave examined. Liquid came from them of course, and in 

 some cases it had a sUghtly milky appearance, but it was never possible to distinguish 

 the milt derived from the testes from the urine coming from the urinary bladder. It 

 was therefore useless to squeeze a male sole over a bottle containing ova in order to 

 fertilise them, for it was impossible to know whether any milt entered the bottle or 

 not. I dissected out the testes themselves from several specimens, and cut them in 

 half and crushed them between my fingers, and found that all the liquid that came 

 from them was thin and almost clear, only very slightlj^ turbid. It is evident, therefore, 

 seeing that these testes came from ripe males, that the sole does not produce any milk- 

 white thick secretion such as constitutes the milt of other fislies. The milt of the sole 

 is not only very limited in quantity, but is a thin liquid only slightlj^ turbid, which is 

 difficult to distinguish when the male is squeezed. A considerable number of soles 

 were taken on this excursion. Some of the females were spent, some unripe, some 

 yielded only about a dozen ripe ova. But one female, the largest specimen I ever saw 

 (see page 126) yielded several thousand ripe ova. The ovaries of this specimen con- 

 tained ripe ova only : she was at the last stage of spawning, and probably these ripe 

 eggs were nearly half the entii'e number produced that season, the rest having already 

 been shed. Having fully investigated the males I concluded that the onW method 

 likely to ensure fertilisation was to extract testes from the male soles, and crush these 

 up into a pulp between my fingers in the water into which the ova were to be allowed 

 to fall. In this way the whole of the milt contained in the male organs was sure to be 

 set free in the water containing the ova. I found this method perfectly successful. 



At the Laboratory there was now a constant circulation of sea-water, and apparatus 

 for hatching floating ova which had been found to work admirably. The year before 

 the Aquarium was unfinished and there was no constant supply of sea-water. I landed 

 at Penzance with fertilised soles' eggs on the morning of March 23. The eggs were 

 contained in short wide glass jars such as are used for conveying sweets: over the 

 mouth of each was tied silk bolting cloth to prevent the eggs escaping, and this, to 

 some extent, prevented the water splashing over. I placed the bottles, held in a 

 divided basket, in the break-van of a train, and took them to Plymouth, where I arrived 

 the same evening. The eggs were at once placed in the hatching jars; they seemed 

 quite healthy, and n\icroscopic examination showed that they were all fertilised. 



The apparatus and method I adopted last spring for hatching floating eggs were as 

 follows : — The apparatus is a modification of that recommended by H. C. Chester, of the 

 United States Fish Commission.* The arrangement of Chester's apparatus is represented 

 in Fig. E {]). 132) : it consists of a tall glass jar, j, which has an open narrow neck 

 above and is widely open below. This is placed in a tank having a constant supply of 

 sea-water, the overflow of which takes place through a siphon tube, s, having a diameter 

 greater than that of the inflow. The water in the jar is of course alwaj-s at the same 



Vide " Devel. Osseous Fishes," by J. A. Ryder, Rep. U. S. Fish Commission for 1885, p. 499. 



s 2 



