[mcmurrich] SCALE-MARKINGS OF THE HALIBUT 35 



Nevertheless four (9-12) or possibly five narrow bands in which the lines 

 are still closer together may be indistinctly seen in this zone, apparently 

 indicating that it represents the growth of as many years, during which 

 there was a considerable disturbance of the normal growth processes, 

 probably to be attributed to a prolonged period of sexual maturity. 

 If the enumeration of the winter zones be correct the periphery 

 of this indistinct zone represents at least the twelfth winter of the 

 life of the fish and it is followed by a final zone of consideral)le 

 breadth, in which the lines have the spacing typical of summer 

 growth; this may be taken to represent the twelfth summer in which 

 the fish was captured. 



If then the evidence supplied by the scale markings of this fish be 

 summed up, its life-history was probably as follows: — It was hatched 

 from an ovum spawned in 1900 and for a period of seven years its 

 metabolic activities were principally devoted to bodily growth, so that 

 by the summer of 1907 it had reached a length of between 60 cm. and 

 70 cm., if the size of the first fish described may be taken as typical 

 for fish of this age. Throughout this period the scale markings show 

 no evidence of reproductive activity, unless the slight irregularity in 

 the fifth year represents a precocious and transitory exhibition of it; 

 but in the eighth year, 1908, a spawning period began, which lasted, 

 apparently without any decided interruption, throughout the succeeding 

 four or five years. During this period the growth of the fish proceeded 

 at a much slower rate than formerly, but with the beginning of 1912 

 the spawning ceased and a period of very rapid growth began, lasting 

 until the fish was captured in the summer of that year. 



I desire to emphasize the fact that this life-history must be regarded 

 to some extent as a tentative one, owing to the small amount of satis- 

 factory material at my disposal. But the reliability of the scale mark- 

 ings as indices of the various phases of growth in other fish is so well 

 established, that I have ventured to assume their reliability in the 

 present instance and to interpret them in accordance with the exper- 

 ience derived from the study of other fish, hoping thereby to establish 

 a working hypothesis as to the life-history of the Halibut, which may 

 serve as a basis for future observation. 



There still remains for consideration a third fish, measuring 152 

 cm. in length, and its scales reveal the same history up to the eighth 

 winter band (Fig. 3), a regular alternation of winter and summer 

 bands without any irregularities that might be ascribed to a spawning 

 period. Beyond the eighth winter band, however, the story seems to 

 differ a little from that of the preceding fish. The next two winter 

 bands (9, 10) are much closer together than either those that precede 

 or those that follow them, the indications being that during the eighth 



