2 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



learn from careful preparations of specimens in, transition stages whether 

 there was merely a mechanical twisting of the facial region in an other- 

 wise normal fish, or a more elaborate rearrangement of the parts with 

 reference to each other, and especially whether any histological clianges 

 accompany the more obvious external modifications. 



II. Material. 



The most of my work has been on the so-called winter flounder 

 (Pscudopleuronectes americanus Walbaum), a dextral ilatlish, but I 

 have also used for the sake of comparison a sinistral species, the 

 sand-dab (Bothus maculatus Mitchill). 



My material was all collected at Wood's Hole, Mass., during the years 

 1898 and 1899. I obtained a series of developing eggs and young 

 Pscudopleuronectes from the hatchery of the United States Fish Com- 

 mission in April, 1898. Adult fishes can be taken by nets at any time 

 through the year. The larval stages at or about the time of the 

 migration of the eye are to be obtained during the month of Juno 

 only. Early in the month only a few are at the point of assuming 

 the adult position, and after June 20th, all the fish of this species taken 

 were already metamorphosed. 



These larvae were caught by surface towing with a coarse scrim tow- 

 net near the wall of the "outer basin" of the U. S. F. C. wharf during 

 the rising tide. They are most abundant on clear days when the wind 

 is on shore and the tide comes in from the east. On very calm or very 

 rough days they are not plentiful. My most successful skimmings 

 were made early in June, and twice I obtained as many as 100 young 

 fish during the inward flow of tlie current (3-4 hours). I was able to 

 save a few of the young fish alive by frequently emptying the tow-net 

 and placing the uninjured specimens in as pure water as possible. 



In the summer of 1898 the sand-dab larvae were taken more abun- 

 dantly than the winter flounders, while in 1899 the winter flounders 

 were about ten times as niunerous as the sand-dabs. 



I kept the young fish in the " outer basin " ^ in large lamp chimneys, 



1 The granite inclosure for the protectioiv of smaller boats belonging to tlie 

 United States Fish Commission is divided l)y projecting parts of tlie dock into the 

 " inner " and " outer " basin. Tiiere are numerous openings in the stone walls to 

 allow the free circulation of the water, and near one of these the float was 

 moored, thus securing as nearly normal conditions of water and food as consistent 

 with protection from violent wave action. 



