THE LIFE-HISTORY OF THE SALMON. 287 



Young Salmonoids, about a foot in length or somewhat less, 

 the size of a Herring,* however, were caught in the Herring nets 

 in August, and this fifty miles from shore. Such an occurrence 

 affords little information, however, as to the numbers in an area, 

 for only those of a suitable size are meshed ; and in many cases 

 the capture of the adults by liners and trawlers is not reported. 

 Mr. Calderwood,t H.M. Inspector of Salmon Fisheries, alludes 

 to several captures at sea by trawlers, and the experiments 

 which are being carried out by him in marking Salmon obtained 

 in bag-nets at sea will, it is hoped, considerably add to our 

 knowledge in the near future. Salmonoids considerably larger 

 than Smolts are occasionally captured in numbers in the 

 estuary of the Tay, so that such forms must linger now and 

 then inshore. 



Whilst food is thus generally absent from the alimentary 

 canal of the Salmon, parasites are plentiful. Numerous tape- 

 worms occupy the pyloric cseca, and threadworms crawl for- 

 ward into the stomach on the death of the host, or are coiled on 

 the surface of the viscera and mesentery. Distomes press their 

 soft bodies amongst the mucus, their pale fluid passing back- 

 ward and forward, becomes stationary and again proceeds. 

 Echinorhynchi are attached to the wall of the stomach by their 

 proboscides. In the duodenum are many larval Distomes, 

 which move actively in the mucus. 



In connection with the circulation and respiration there is 

 little differentiation from the ordinary Teleostean. It is worthy 

 of note, however, that in the young fish the first vessels to leave 

 the line of the body are those passing into the "fatty" fin; 

 whilst in fresh water the gills have the parasite Lemceopoda 

 salmonea, which is killed when it enters the sea, just as the 

 external parasite Lepeophtheirus salmonis disappears in fresh 

 water. No young fish is better adapted for experiments on the 

 circulation than the Salmon, whether in connection with the 

 effect of drugs and poisons, or the behaviour of the capillaries 

 after operations. The presence of a dilatation on the caudal 



* There may have been many larger and smaller accompanying the 

 forms caught, the heads of the former being too large for entering the 

 mesh, whilst the smaller heads might slip out. 



t Vide ' S. F. B. Salmon Fisheries,' 1913, No. 1, pp. 4 et seq. (1914). 



