2 ESDAILE, Scales of three Specimens of Salvio salar. 



the sea. The scales of small summer or autumn fish show 

 this same arrangement with the addition of a third period 

 of rapid increase, varying in size according to the date of 

 capture. The large spring fish show rapid and slow 

 growths alternating three times. 



Mr. Johnston proves all these results by examining 

 the scales of fish which had been previously marked when 

 they were migrating to the sea as smolts. He also proves 

 that a fish which has entered the river for spawning 

 purposes has a very distinct and indelible mark on its 

 scales. Almost as soon as a spring or early running 

 summer fish reaches the river, the scales begin to 

 disintegrate at the periphery, and by the time the fish is 

 a kelt a very considerable portion of the surfaces and 

 periphery of the scales has disintegrated, and in most 

 cases the scale has the appearance of being much worn 

 and frayed. In the case of late running summer and 

 autumn fish, this disintegration also takes place in salt 

 water, and before the fish has entered the river. On 

 returning to the sea the fish begins to feed again ; the 

 new growth of the scale is regular and is in great contrast 

 to the irregularities caused by this disintegration, so that a 

 very clearly defined mark is made, which Mr. Johnston 

 has termed the " spawning mark." 



Herr Dahl confirms all Mr. Johnston's work, and 

 shows that the marks on the scales of Norwegian salmon 

 are formed in a similar manner to those on the scales of 

 Scottish salmon. He made careful investigations as to 

 the " spawning mark " and the extent of the degeneration 

 of the scales while the fish are in the river before spawning. 

 The rest of Herr Dahl's work on the salmon shows us in 

 how many ways the knowledge of the age of the fish from 

 its scales can help us in discovering more about the 

 life-historv of the fish. His work is full of most 



