100 MK J. T. CUNNINGHAM ON THE 



The anus is open ; notochord multicolumnar ;' ;: " small round pigment spots along 

 the sides and head ; pelvic fin not developed. 



On March 5 of the current year I visited some fishing boats at Kincardine 

 on the Forth. These boats were fishing with what are called bag-nets or stow- 

 nets. A net of this kind is fashioned very much like a beam-trawl, and is 

 fastened beneath the boat, so that its mouth faces the current of the tide ; the 

 fish are thus washed into the net. Among the fish taken on the occasion of my 

 visit were a large number of Pleuronectes Jlesus, which are commonly called 

 fresh- water flounders, or mud flounders. Nearly all of these fish had a number 

 of small round white tumours on the fins and on the upper or dark side. 

 The tumours are cutaneous, and have been described more than once (see 

 M'Intosh, Third Annual Report of Scottish Fishery Board). The fishermen 

 stated that these tumours were the eggs of the fish, that the mud flounder 

 carried its eggs on its back. On another occasion a bottle was sent to me from 

 Elie, said to contain flounder spawn ; the contents when examined proved to 

 be the greenish gelatinous egg-cases of some species of Chsetopod, perhaps 

 Arenicola piscatorum, and within the cases were the trochospheres, whose green 

 colour was the cause of the colour of the cases. 



5. Pleuronectes limanda, Linn. (Salt-water Flounder) (PI. II. figs. 9-11; 



PI. III. figs. 1-6). 



Ripe specimens of this species were obtained by me in considerable 

 numbers on board a steam-trawler six or seven miles east-north-east of the Isle 

 of May, on May 21 of the current year. A number of the eggs were squeezed 

 out, artificially fertilised, and conveyed to the Marine Station. Living specimens 

 were also successfully carried to the aquarium, and upon eggs taken from these 

 I was able to study the condition of the ripe eggs immediately on their escape 

 from the oviduct, and the earliest processes of fertilisation and development. 



The egg, after the formation of the perivitelline space, is '84 mm. in diameter; 

 the appearance, magnified 33 times at the close of simple segmentation, is 

 shown in PI. II. fig. 9. 



Hatching took place on the third day; the temperature of the surface of 

 the sea where the eggs were taken was 7° 5 C, and the temperature of the water 

 containing the eggs varied from this to 10° C. 



The newly hatched larva was 2*66 mm. in length ; the structure closely 

 similar to that of other species of the genus; notochord multicolumnar ; mouth 

 not open; small black pigment spots on sides of the body; anus close to the 

 yolk, and not open. 



* The terms unicolumnar and multicolumnar applied to the notochord refer to the arrangement of 

 the vacuoles, which are very conspicuous in newly hatched fish : in the herring and a few other cases 

 these vacuoles arc cubical, and form a single linear series ; in other cases there are several series. 



