Manchester Memoirs, Vol. hi. (191 2), No. JJ. 3 



interesting results, and great thanks are due to the 

 Salmon and Trout Association for arranging for the 

 immediate publication of an English translation, which 

 will be of great assistance to the numerous workers 

 engaged on the study of the life-history of the salmon. 



Before going further into previous work, it will be 

 advisable to give names to the different parts of the scale, 

 in order that misunderstanding may not occur. Already 

 the terms "annual lines," " ridges," " rings," and "lines" 

 have become confused. Although many descriptions of 

 the scale have been given, one more is now added to that 

 number for the purpose of introducing the names I 

 propose to use. The scale is lamina-like, the internal 

 side is smooth, but on the external surface there are 

 inequalities which can be readily felt on passing a needle 

 over the scale. On closer examination it will be found 

 that the inequalities are caused by what have hitherto 

 been called " lines " or " ridges," but which I shall term 

 annuli (see photo of Scale A). These annuli are arranged 

 in a roughly concentric manner from the centrum of the 

 scale (C), and are formed chiefly on the anterior portion of 

 the scale, which is enclosed in a pocket of skin, but also, 

 to a very slight extent, on the posterior exposed portion. 

 Examination with the low power of the microscope shows 

 that the annuli are arranged in a definite manner, some far 

 apart and others closer together. Those far apart are, 

 according to Mr. Johnston, formed during the rapid growth 

 of the fish in the summer, and those closer together during 

 a time of slow increase in the winter. This formation of 

 annuli far apart, together with the formation outside this 

 of annuli more closely placed, was called by Mr. Johnston 

 an "annual ring." For this name the word " Peronidium " 

 is substituted, and it is used to indicate the growth which 

 takes place in a complete summer and winter. 



