NOTES AND MEMORANDA. 625 



pigment in their case was that of the flounder; the blastopore 

 closed in the usual way, but the short larva was coiled round 

 the yolk-sac in an unnatural manner. The organs of the body were, 

 however, well developed, and the eyes later assumed their black pio-. 

 ment. These larvse were able to move about in the water but 

 sluggishly, and died within a few hours. 



On the 15th February the converse experiment was tried; the 

 ripe eggs of the flounder were fertilised by the milt of the plaice. 

 During the first few days the mortality was very great, but a week 

 later several thousands were still alive and in a healthy condition. 

 The blastopore was completely closed, and the caudal region was 

 beginning to separate off from the yolk ; the eyes were formed, and 

 the pigment over the embryo was that of the flounder. A good 

 many died in the later stages within the egg, but a considerable 

 number hatched out and lived for several days, although the water 

 had not been changed for a fortnight. The larvse which hatched out 

 were a little larger than the ordinary flounder larv?e at that stage, but 

 were in other respects like the flounder. They were strong and active, 

 and did not seem in any way less capable of development than ordinary 

 larvse reared under similar conditions. 



On the 5th March a flat-fish was brought to my notice by some 

 fishermen at Brixham. In their opinion it was a flounder, but they 

 were somewhat puzzled by its smooth appearance and slightly different 

 shape. On examination, it was found that so far as external characters 

 went it was more nearly a plaice. The fin-ray formulae were too high 

 for the flounder, and the characteristic plaice tubercles were present on 

 the head, whilst the rough spines of the flounder were absent. The 

 only resemblance to the flounder was in its small, closely-set scales and 

 coarse-looking skin, which was much darker than is usual in the plaice, 

 even from deep water. The specimen was 17 inches long and was 

 full of roe. The ripe ova were obtained from it readily, and even to 

 the naked eye appeared much smaller than the normal plaice ova. On 

 examining them under the microscope, they appeared clear and trans- 

 parent like normal ova. Under a high power the characteristic 

 corrugations of the capsule of plaice eggs were seen. Their size, 

 however, was abnormally small. Of fifty whose dimensions were taken, 

 none exceeded 1-3 mm., and the majority were nearer 1-2 mm. These 

 were representative of the rest in the ovary. The ordinary size of 

 plaice eggs lies between 1-6 and 1-8 mm., so that from this character 

 alone one might infer some mixture of plaice and flounder. 



DESCRIPTION OF PLATE III. 



Fig. ]. — Abnormal Tub ( 7'. lucerna.) 



Fig. 2. — Post-larval Pleuronectid (P. cynoglossus or H. vulgaris). 



Fig. 3. — Scale from eyed side of young Topknot (Z. punctatus). 



