840 PROFESSOR W. C. M'INTOSH AND MR E. E. PRINCE ON 



with those on the ventral margin as well as the head. Pigment-specks persist at the 

 base of the tail. The body is now proportionately broader. 



In specimens 2 mm. or 3 mm. longer, similar features as regards pigment and other 

 points occur, but the left eye is mounting over the head, and the ventrals appear as 

 minute buds, while the marginal fins of the specimens are still infested by young Caligi. 



These specimens were generally procured E. or S.E. of the Island of May, in water 

 varying from 18 to 29 fathoms, the mid- water net being floated about 4 fathoms above 

 the bottom. 



The earlier stages of this species have been observed by Mr J. T. Cunningham,* who 

 secured the ripe adults in June by the trawl near Cumbrae in the Clyde. His oldest 

 larva, however, represents a considerably younger stage than our fig. 7, PI. XVIII. , the 

 latter being about 8 mm. in length, whereas Mr Cunningham's earlier form (rather more 

 than two days old) measured 5*9 mm. Moreover, instead of three dark patches, there 

 are four on the tail. It is satisfactory to have a fairly complete series of this species, 

 which, on the eastern shores, is generally characteristic of deep water. Mr Cunningham's 

 ova hatched on the 6th day, but they were under abnormal circumstances as regards 

 temperature. 



Pleuronectes platessa, L. — The ova of the plaice (which measure "065 to '069 in.,t or 

 1*65 to 17 mm.) were brought by Captain Burn, late of the 11th Hussars, on the 21st of 

 April, having been fertilised two days before. The zona radiata is minutely punctured, 

 and it is often peculiarly wrinkled. On the 28th the embryo is clearly outlined, and is 

 conspicuous by its bright canary-yellow spots (PI. V. fig. 6). The spots do not extend 

 quite to the tip of the tail, but leave a considerable terminal portion bare. In one speci- 

 men a vesicle (kv), similar to Kupffer's, appeared in the mid-abdominal region, and was 

 thus considerably in front of the normal position. It possessed a distinct protoplasmic 

 covering. Moreover, a smaller vesicle appeared on the surface of the protoplasm of 

 the larger. The heart of the young plaice presents the same features as in other pelagic 

 forms, and begins to beat on the 6th day, and at 7.30 p.m. on the 28th April it pulsated 

 forty times per minute. Its long tubular region lies to the left side, goes forward and 

 forms a loop, turning backward just as in larval round fishes. The great breadth of the 

 marginal fin is noteworthy, and it is well seen in the egg. In several examples film-like 

 bands or ridges stretch across obliquely from the head of the embryo into the rest of 

 the blastodermic area. As the pigment develops in the eyes some are finely iridescent, 

 with a reddish-golden lustre, but in a day or two the silvery sheen surrounds the pupil. 

 The eggs are hatched in nine or ten days, and the larva is conspicuous amongst its 

 congeners, the flat-fishes, by its great size (PI. XVI. figs. 5, 5a). This does not imply 

 that it is more readily observable, for the larvae are difficult to discern in the water. 

 When about a week old the canary-yellow colour seen so distinctly posteriorly is found 

 to be due to rounded corpuscles, which by transmitted light appear to be brownish, 

 and more or less opaque. The marginal fin of the larva is of great breadth, though in 



* Op. cit., p. 101, pis. iii., iv., and v. t Mr Cunningham (op. cit.) gives T95 mm. 



