NOTES AND MEMORANDA. 196 



Andrew's Bay ; lie obtained them from fishermen's haddock-lines 

 (Ann. and Mag. Nat. Hist., August, 1891).— J. T. C. 



Breeding of Fish in the Aquarium. — At the end of March the 

 plaice in the large flat-fish tank were spawning, and the eggs 

 floated at the surface of the water. But when examined, none of 

 the eggs were found to be fertilized. A hatching box of Captain 

 Dannevig's pattern had recently been fitted up in the aquarium for 

 hatching floating eggs. I took out some of the ripe plaice and 

 fertilized a number of eggs from them artificially. Some of the 

 females yielded healthy eggs, and large numbers of these were suc- 

 cessfully hatched in the hatching box. But some of the females 

 yielded only ripe eggs which were already dead ; the difference 

 between these and unripe eggs being perfectly obvious. These same 

 plaice spawned in the tank in 1890, and the eggs were naturally 

 fertilized and found in a developing condition at the surface in the 

 tank. It seems as though a prolonged residence in the water of 

 the aquarium produced some abnormal disturbance of the reproduc- 

 tive functions in these plaice. In the same tank were two ripe 

 female flounders, but no males of the same species. I squeezed a 

 large number of eggs from these, and made the experiment of 

 mixing them with milt from a male plaice. Fertilization occurred 

 in a certain number of the ova, about half, and a few of these lived 

 till they were hatched, and the larvae lived several days. They 

 died, however, like all my larvae, soon after the absorption of the 

 yolk-sac. In April and May many of the soles in the flat-fish tank 

 were much swollen in the abdominal region, and it seemed as if the 

 ovaries ware enlarged and the eggs on the point of being shed. 

 But no soles' eggs ever appeared in the tank, although arrange- 

 ments were made that no floating eggs shed in the tank could 

 escape. After a time many of the soles gradually lost the swollen 

 appearance. I took out a specimen 25 cm. long on June 10th, and 

 found it was a male, and on teasing up a portion of the testis saw 

 a considerable number of ripe active spermatozoa mixed with 

 unripe spermatic cells. Afterwards I squeezed a swollen female, 

 but no ripe eggs were expelled, but, instead, some curious translucent 

 masses whose nature I did not understand. On June 27th I took 

 out a large female sole which was still swollen, and on squeezing 

 obtained some more of these masses of soft substance. "When 

 teased up under the microscope the substance proved to consist of 

 degenerate ripe ova, looking as though they had been half 

 digested. The vitelline membranes were present, but shrivelled and 

 containing only granules of dead matter. I then opened the ovary, 

 and found more of these masses in its cavity ; the ovary itself was 



NEW SERIES. VOL. II, NO. II. 16 



