108 THE TEKIODIC GROWTH OF SCALES IN GADID/E 



EXPLANATION OF PLATES. 



Plates I. to IV., Photo-micrographs of Scales of Pollack. 

 Plate v., Scales of Poor Cod. 

 Plate VI., Scales of "Whiting. 



Plate VII., Fig. 1, Scale of Whiting ; Fig. 2, Scale of Coal Fish (Gadus rireuf^). 

 Plate VIII., Fig. 1, Scale of Haddock ; Fig. 2, Scale of Norwegian Whiting Pollack 

 (Gadus Esmarkii). 



The lettering is taken in each case from the posterior area of the scale. 



C = Centre of growth. 

 C - W 1 = Growth of first year. 

 C - S 1 = Growth of first summer. , 



S 1 - "W 1 = Growth of first winter. 

 W 1 - S 2 = Growth of second summer. 

 W 1 -W 2 = Growth of second year. 

 W 2 - W 3 = Growth of third year. 

 L.G. = Lines of growth. 

 S.L.G. = Summer lines of growth. 

 W.L.G.= Winter lines of growth. 



o*- 



PLATE I. 



Fig. 1.— Scale of young Pollack, 3 to 4 months old, magnified about 140 diameters. 

 Length of fish, 5-4 cm. (2-12 in.) ; date of capture, July, 1901. Scale shows three 

 lines of growth. The figure was drawn with the aid of the camera. 



Fig. 2. — Scale of Pollack, 7 to 8 mouths old, magnified aljout 45 diameters. 

 Length of fish, 10-15 cm. (3-99 in.) ; date of capture, December 4th, 1889 ; number 

 of lines of growth, 18. The later lines are clo.ser to one another than the earlier, 

 indicating winter growth as distinguished from summer growth. The distance 

 between two consecutive summer lines of growth is seen, from the Figures 2, 3, 

 and 4, to be in some cases half as much again as the distance between two con- 

 secutive lines of winter growth ; in other cases it may be twice as great. 



Fig. 3.— Scale of pollack, 7 to 8 months old, magnified 45 diameters. Length of 

 fish, lO'O cm. (3'93 in.) ; date of capture, December, 1889. Shows 20 lines of growth. 



Fig. 4. — Scale of Pollack, 7 to 8 months old, magnified 45 diameters. Length of 

 fish, ir7.') cm. (4-62 in.); date of cajjture, December 4tli, 1889 ; number of lines of 

 growth, 20. The later lines are closer to one another than the earlier lines, indicating 

 winter growth as distinguished from summer growth. 



Fig. 5.— Scale of Pollack, 1 year 2 to 3 months old, magnified 37^ diameters. 

 Length of fi.sh, 2476 cm. (975 in.); date of capture. May, 1902; number of lines of 

 growth first year, 2G, 8 lines the early growth of the second year. 



PLATE II. 



Fig. 1. — Pollack scale at end of second summer, magnified 45 diameters. Length 

 of fish, 28-5 cm. (11'22 in.) ; date of capture, October, 1900; age determined, 1 year 

 6 to 7 months. 



Fig. 2. — Pollack scale at end of second year. Length of fish, 3365 cm. (13"25 in.); 

 date of capture. May, 1902. This photo-micrograph has, owing to the larger size of 

 the scale, been magnified much less than jireceding scale. 



