386 SELIG HECHT 



in their work on the plaice. Since that time, weight-length 

 coefficient has been used mainly in the study of the European 

 plaice by Johnstone ('14) and others. - 



Thus, at least eleven different species representing seven dis- 

 tinct families, have been investigated for this relation. It seems 

 therefore safe to conclude that in fishes generally the correlation 

 of weight to length is such that the weight is equal to a con- 

 stant factor times the cube of the length: — 



weight = a X (length) ''. 



It is to be expected that there will be a seasonal variation in 

 the value of this coefficient corresponding to the cyclic physio- 

 logical changes that the species undergoes in the matter of nutri- 

 tion and reproduction. Indeed, Johnstone ('11) states that the 

 value of a varies during the different seasons of the year, and 

 furthermore, that this coefficient is the only convenient index 

 of the 'condition' of the plaice inhabiting any given fishing 

 ground. When the plaice is well nourished or sexually ripe, the 

 value of a is large, whereas, when the fish is ill nourished or spent, 

 the value of the coefficient is low. Generally speaking, it is 

 greatest in the summer and least in the winter (especially, John- 

 stone, '14, fig. 5). 



It was this variation that caused the failure of Hensen and 

 Reibisch in their early attempts to get at this constant. 



BODY MEASUREMENTS 



These results suggest (Hecht, '13) that the form of an indi- 

 vidual fish is constant, within rather narrow limits, throughout 

 its life (Spencer, '71, p. 123). To study this in detail, I examined 

 the relations among the morphologic surface divisions of each 

 species. Since the relation of weight to length is known and is 

 constant, length was chosen as the unit of comparison among 

 the parts studied, viz., the length of head, body, and tail, and 

 the width and depth of the animal. 



The head-length in all species means the distance from the 

 tip of the snout to the end of the opercular bone. The body- 



- When Crozier and I found the same relation for the weakfish, we were entirelj- 

 unaware of this European work on the plaice. It was only after the present work 

 was completed that these contributions came to my attention. 



