60 THE TERIODIC GEOWTII OF SCALES IN GADID^E 



(3) That the length of the axis AB^ or AB" (axis from centre of 



growth to posterior end of scale) increases in a correspond- 

 ing way. 



(4) That in young fisli the broadest scales are those taken from the 



median region of tlie lianks (second region) ; but in the case of 

 the older fish the broadest scales are those from the third 

 region, namely, vertically beneath the second dorsal fin. 



I have selected that region vertically beneath the first dorsal fin as 

 the area from which I usually take scales for examination for several 

 reasons : firstly, that it is the area from which previous workers have 

 taken scales ; secondly, that this is, according to Klaatsch, Ussow, etc., 

 the region in which scales first develop ; thirdly, that in the case of 

 fish in which the scales have been rubbed off by mechanical friction, 

 this area appears to retain them longer than others. This may be 

 because it is partly protected by the pectoral fin. 



