AS AN INDEX OF AGE. 109 



PLATE III. 



Fig. 1. — Scale of Pollack at end of second year. Length of fish, 33"G5 cm. 

 (13-25 in.) ; date of capture, May, 1902. This scale has been photographed because 

 it shows extremely little growth for first year, namely, only 18 lines of growth, while 

 that of the preceding scale, for example, shows 28 during this period. 



Fig. 2. — Scale of Pollack at commencement of fourth summer, magnified 28 

 diameters. Length of fish, 4440 cm. (17-50 in.) ; date of capture, April 30th, 1901 ; 

 age determined, 3 years 6 weeks. 



PLATE IV. 



Scale of Pollack at commencement of ninth year. Length of fish, 78-74 cm. 

 (31 in.) ; date of capture, April or May, 1902. This photo-micrograph shows, firstly, 

 how it becomes a much harder task to distinguish the annual rings in the scales of 

 older and larger fish, and, secondly, that the scales of such tend naturally to become 

 broken and disintegrated. Age determined, 8 years 6 weeks. 



PLATE V. 



Fig. 1. — Scale of Gadus minutus in its second summer. Length of fish, 14-30 cm. 

 (5-62 in.) ; date of capture, July 9th, 1901. This scale shows very clearly the earlier 

 growth of second summer. First year, 37 lines of growth ; second year (early 

 summer), 9 lines of growth. Age determined, 1 year 3 to 4 months. 



Fig. 2.— Scale of Gadus minutus at end of third winter. Length of fish, 19-05 cm. 

 (7-50 in.) age determined, about 3 years. 



PLATE YI. 



Fig. 1.— Scale of Whiting in its second summer. Length of fish, 28-50 cm. 

 (11-22 in.) ; date of capture, July 16th, 1901. This scale shows 29 lines of growth 

 for the first year, and 14 lines of growth for the second summer up to July 16th. 

 Age determined, 1 year 4 to 5 months. 



Fig. 2.— Scale of Whiting towards end of the fourth year. Length of fish, 

 34-0 cm. (13-38 in.) ; date of capture, January 10th, 1902. This scale shows the 

 following lines of growth : first year, 31 ; second year, 21 ; third year, 10 ; fourth 

 year, 9. Age determined, 3 years 10 months. 



PLATE YII. 



Fig, 1. — Scale of Whiting at commencement of fifth summer. Length of fish, 

 49 cm. (19-29 in.) ; date of capture. May 14th, 1901. Age determined, 4 years 

 2 months. 



Fig. 2.— Scale of Coal Fish {Gadus virens) in the early summer of second year. 

 Length of fish, 20-22 cm. (8 inches). This scale shows very clearly the early growth 

 of second summer. 



PLATE VIII. 



Fig. 1. — Scale of Haddock at commencement of third summer. Length of fish, 

 26-25 cm. (10-33 in.) ; date of capture. May 10th to 15th, 1901. This scale shows 

 21 lines of growth for the first year, and 20 lines of growth for the second year. 

 Age determined, 2 years. 



Fig. 2.— Scale of Norwegian Whiting Pollack {Gadus Esmarkii) in its third 

 summer. Length of fish, 19-05 cm. (7-50 in.) ; date of capture, August 27th, 1900. 

 Age determined, 2 years 3 to 4 months. 



As to the photo-micrographs, Figures 2, 3 and 4, Plato I., were taken by myself ; 

 the remainder are the work of Mr. L. E. Sexton, Plymouth, and Mr. A. Flatters, 

 Manchester. 



