624 NOTES AND MEMORANDA. 



Better examples of marine forms are found in the so-called turbot- 

 brill and brill-turbot which Smitt* describes. Such specimens are 

 far from uncommon, and have been mentioned by various naturalists. 

 Holt,-]- into whose hands several specimens came, carefully reviews 

 their characteristics, and points out, in addition to their intermediate 

 character, that his specimens, though large, were still sexually im- 

 mature. He was inclined to consider them as hybrids between a male 

 turbot and female brill. 



During the past year a few observations have been made on this 

 matter, which seem to call for brief notice here. 



On the 25th January, 1902, several thousand eggs of plaice were 

 fertilised by the milt of a flounder, both running, and as only a few 

 died during the first few days, the fertilisation must have been success- 

 ful. Development proceeded very slowly until the 6th February, when 

 the eggs were transferred to the tanks at the Laboratory. At this 

 time the embryo was half-way round the yolk. Development then 

 became rapid, due to the higher temperature, and many embryos were 

 endeavouring to hatch on the 8th. The great majority died during this 

 process, and the few that managed to escape died within a few hours. 



Experiments which were going on in the Laboratory at the same 

 time with another batch of eggs from the same plaice, but fertilised 

 by the milt of a plaice, had no better success, and it may be that 

 there was something wrong either with the eggs originally or in the 

 surrounding conditions. Nevertheless, the phenomena displayed during 

 the development of the hybrids are worthy of record. 



The colouring of the embryos generally was that of the plaice ; the 

 length of the few larvse which hatched was from 3-5 to 4 mm., being 

 little more than half that of the ordinary plaice larvae; the yolk-sac 

 was 2 mm. long, so that, as may be imagined, the tail of the larva 

 was extremely short. This had probably a great deal to do with their 

 inability to break through the egg-capsule. Further, instead of the 

 tail being straight, it was curved round the yolk-sac; in fact, if we 

 imagine a small flounder larva with plaice markings, foisted off on 

 a large plaice yolk-sac, we have the exact appearance of these larvte. 

 The male element seemed to affect the length of the larva, which 

 in other characteristics followed the female; the blastopore, also, 

 was never completely closed, a round, circular opening on the posterior 

 aspect of the yolk-sac being plainly visible. Consequently, on hatch- 

 ing, the yolk-sac was soon ruptured by the entrance of sea-water. 



Only two embryos were exceptions to the above. These did not 

 hatch until three days later — namely, on the 9th February. The 



* Scandinavian Fishes, vol. i., p. 444. 

 t Joiirn. M. B. A., vol. iii., 1895, p. 292. 



