392 SELIG HECHT 



mined directly from the curves, and is taken from the paper 

 ah-eady referred to. 



TABLE i 



Values of K 



Urovoortui lyrannus 0.336 



Ancho via browni i . 549 



Anchovia initcliilli 0.475 



Pcprilus alopidotus 0.350 



CynoHcion rogali.s 0.565 



Lciosloinus xanthurus , 0.468 



Orthopristis chrysopterus 0.467 



RATE OF OROWTH 



Tn the paper on the weakfish it was stated that the 'tangents' 

 of the Hnes, such as those in figures G to 10 (collected in table 3), 

 indicate the rates of growth of the various parts relative to the 

 total lem/th. This statement as modified by the italicized phrase, 

 is coi'rect, because the values for the constant c indicate the entire 

 number of units ac(iuii-ed by a given part per unit acquisition 

 by the total length. 



Strictly speaking, however, these values do not represent 

 rates of growth, and the above suggestion is likely to be misin- 

 terpreted to mean that the real rates of growth of the various 

 parts are different. The rate at which a body or an organ 

 grows, is the number of units ac(iuired in a given unit of time, 

 divided by the numbei- of units alreatly there (Minot, p. 93), 

 Applying this definition to the matter under consideration, it 

 becomes evident that the rates of growth of all parts of the 

 fish are identical. 



This may be shown graphically by means of figure II. In 

 A the total length of a hypothetical fish is represented by 20 

 units, the head being represented by 4 units, the body by 10 

 units, and the tail l)y (> units. ^ The ratio of head to length is 



•' I'hc.sc units iiavc no morphologic significance, i.e., they do not represent 

 scales, because the number of scales is constant for any individual; nor arc 

 they to be interpreted as representing cells. Compare in this connection the 

 work of Berezowski ('10) on the size of cells in a growing organism, Morgulis ('11) 

 on the size of cells during decrease of body size through inanition, of Morgan 

 ('95 and '96) and of Driesch COO) on the size and number of cells in embryos 

 from isolated blastotneres, and of Conklin ('12) on cell size and body size. 



