LIFE-HISTORY OF AMPHIGONOPTERUS AURORA. 197 



TABLE III. 



SIZE OF YOUNG CARRIED BY FEMALES OF DIFFERENT SIZE AND AGE. 



Number of Lengths of Females Age of Females (End of 



Young. Carrying Young. Given Year syice Birth). 



5 87 I. (j) 



6 76,82 I. (2) 



7 77. 77. 78, 79, Si, 84, 85, 87, 88 I. (9) 



8 77,81,90 I. (3) 



9 84,85,86,88,94; 122 I. (5) ; III. (i) 



10 92, 96, 103 I. (3) 



ii 85,88,91,95,95 I. (5) 



12 92 I. (i) 



13 98, 98, 102 I- (3) 



M 94, 95, 102 I. (3) 



15 99, 103 I. (2) 



16 129 IV. (i) 



17 



l8 122 IV.(l) 



19 96; 123 I. (i) ; III. (i) 



2O 122, 128 III. (2) 



21 



22 121, 128 III. (2) 



23 123 IV. (i) 



24 to 29 - 



30 126 ni.(i) 



SEASONAL MARKS (OR ANNULI) ON THE SCALES. 



During recent years there have been conducted numerous 

 studies, of biological interest and economic significance, based 

 upon age-determinations and the computed rate of growth of 

 fishes. In these studies there has been developed and rather thor- 

 oughly tested a method of age-determination involving an in- 

 terpretation of the seasonal rings indicated in scales, otoliths and 

 certain bones ; the scales have been most widely used. It has been 

 demonstrated, most definitely in the salmonoid fishes, that the cir- 

 culi covering the surface of the scales (cf. Fig. 4) become weaker 

 in structure, more interrupted and more closely approximated 

 during each winter, apparently as a result of the lessened physio- 

 logical activity and retarded growth of the fish at that season. In 

 certain fishes which have been investigated, these winter marks 

 or annuli are indicated not so much by an approximation of the 

 circuli as by a change in their direction and an interruption in 



