6 ESDAILE, Si'n/cs of thr-ec Speciviens of Snlmo snlar. 



aniiulus which crossed the lines on the eye-piece and 

 making no distinction whatever between main or dupHcate 

 branches. By inverting the marked eye-piece, enumera- 

 tions could be made along lines at 30^ on both sides of 

 the long axis. 



This particular fish had, according to the reading of 

 the scale put forward b}^ Mr. Johnston, spent two years 

 and a portion of a third year in the river, and two years 

 and a portion of a third \'ear in the sea, thus showing 

 four peronidia and the beginning of a fifth (see Ih'ni^. 2). 

 However, in registering the number and measurements 

 of the annuli, the river growth has not been merged 

 with that of the sea, but a new division has been made 

 which is used for the portion of the third peronidium 

 formed in the river. Conditions in the river are much 

 more variable than those of the sea, and therefore, when 

 considering the variations in the amount of growth 

 which has taken place, it is advisable to carefully 

 distinguish between the portions of the scale which have 

 been formed in the sea or the river. By making this 

 distinction the divisions of the scale do not correspond 

 to the peronidia, and in the register of the enumerations 

 and measurings the word " period " has been used. This 

 would not be necessary if the young fish had migrated 

 before there was any commencement of feeding during the 

 early part of the third year in the river. The " periods " 

 would then coincide with the peronidia and the word 

 "period" be unnecessary. (See Diag. 3.) 



Table i shows the results of the examination of the 

 scales, one from each of the seven positions on the fish, 

 and it is evident that there is a great amount of 

 variation in the number of annuli on the various scales. 

 It will be noticed that no two scales are alike in any one 

 respect, except that from whatever part of the body they 



