42 



REDUCTION IN THE NUMBER OF FIN-RAYS 

 OF CERTAIN FLAT-FISHES. 



By Philip Cox, Ph. D. 



EVERAL species of two or three p^enera of Pleuronedidse 

 are more or less common in the coast waters of 

 Northern New Brunswick, and the writer has, 

 from time to time, carefully examined many with the 

 object of ascertaining if the type here differs in any re- 

 spect from what it is farther south along the Atlantic. These 

 fishes are among the best for a study of this kind, as they are 

 largely stationary and local, performing no migrations or ocean 

 journeys of any extent. Hence the overlapping and comming- 

 ling of stock of adjoiring regions, which has a tendency to 

 preserve z, uniform type, cannot, in their case, take place on 

 a large scale, so that variation due to temperature, food, and 

 environment is liable to be preserved and intensified from age 

 to age. 



Theclimatal character of the Gulf of St. Lawrence and adjoin- 

 ing bays is peculiar in some respects. In summer the tem- 

 perature of the water of this land-locked gulf, and especially 

 of the Miramichi Bay and Bay des Chaleurs rises higher than 

 that of the coast waters several hundred miles farther south; 

 while in winter the opposite is the case, for the cold is more 

 intense. Fishes frequenting these bays the greater part of the 

 year, and the adjacent gulf waters the remainder, are subjected 

 to extremes of temperature and all it involves to a greater degree 

 than the local fauna of more southern coasts. If then physical 

 and biological conditions of habitat react upon the animal 

 organism and induce modification of primitive structure and 

 habit to be transmitted to descendants, some deviation from 

 more southern type features ought to be found characterising 

 the flat-fishes of this coast. When, however, he began the in- 

 vestigation, the writer is free to admit, he looked for a diverg- 

 ence, if such existed, of a nature the very opposite of what he 



