314 BULLETIN OF THE BUREAU OF FISHERIES. 



to be finely tuberculate. At 15 days hatching had commenced, although comparatively 

 little activity on the part of the embryo had been observed at any time while in the egg. 



Larval development. — On hatching the larva appeared as in figure 275a. In some 

 individuals the eyes were entirely unpigmented, while in others chrome yellow pigment 

 similar to that present on other parts of the body was present in the iris, a type of ocular 

 pigmentation developed by all the larvae within a few days. Later the pupil became 

 generally tinged with greenish, and by the time the larva reached the stage shown in 

 figure 275 b and c, 19 days, the pupil had become black and the iris presented a metallic 

 greenish iridescence. The eyes were directed slightly forward and downward, the 

 mouth was large and functional, and the yolk was absorbed at this stage. The entire 

 animal was perfectly symmetrical as yet. The pigment had become a little darker, 

 approaching a light orange. None of the larvae survived for more than 22 days. 



Preserved material which had been collected at Boothbay Harbor, Me., by Supt. 

 E- E. Hahn near the end of the same season was also examined, and it was found that 

 the development had been quite similar to that of the material studied at Woods Hole. 

 Mr. Hahn succeeded in holding some larvae until the twenty-seventh day after hatching. 

 The chief advancement beyond that condition shown in figure 275 b and c was one of 

 size. These examples, which were preserved in formalin, averaged about 5 mm. in 

 length, while those found to be living at the end of 22 days at Woods Hole averaged 

 about 4.5 mm., which is a trifle over that of the example illustrated by figure 275 b and c. 

 The larvae were held in Chester jars, the mouths of which were covered with a double 

 thickness of cheesecloth. It was difficult to find a screening which would hold the 

 fishes in and at the same time allow smaller food organisms to pass through and permit 

 a sufficient change of water. The cloth employed was far from satisfactory, but fine 

 bolting cloth was found to be entirely unsuitable, as it clogged too readily with diatoms 

 and fine debris. A similar difficulty was reported from the Boothbay Harbor station. 



In 1885, under the name of Pleuronectes americanns Walb., from material studied 

 at Newport, R. I., during July and August, Agassiz and Whitman 2 described and illus- 

 trated the development of what they believed to be this species. It is now apparent, 

 however, that these splendidly rendered illustrations and carefully written descriptions 

 refer to some species of a very different habit. Aside from the fact that the illustrations 

 do not agree with those accompanying the present paper, which have been based on 

 material definitely known to be P. americanus, it is evident, since their material was 

 pelagic and was taken in midsummer, that their work was a study of the development 

 of another fish. It is doubtful, indeed, if the material was of a Pleuronectid nature at 

 all, principally owing to the long gut shown in their plates, which is highly unusual for 

 members of this group. In a previous paper Prof. Agassiz 3 illustrates more advanced 

 stages of some flounder which he also identified as this species, but it is thought that his 

 sketches represent some other form, although the insufficiency of data presented there- 

 with precludes any very conclusive statement at present. 



2 Agassiz, Alexander, and C. O. Whitman: Studies from the Newport Marine Laboratory. XVI. The Development of 

 Osseous Fishes. I. The Pelagic Stages of Young Fishes. Memoirs of the Museum of Comparative Zoology at Harvard College, 

 Vol. XIV, No. r. Part I, 56 p.. XIX pis. Cambridge, :88s. 



•Agassiz. Alexander: Development of the Flounders,. Proceedings, American Academy of Arts and Sciences. Vol. XIV| 

 p. 1-25, pis. Boston, 1879. 



