Fishes. 4789 



Tabular view of the relative proportions — 



1. Of the head; 



2. Of the segment of the body anterior to the anal fin to the length ; 



3. Of the segment of the body beyond the anal fin to the length — 

 in the 



Smolt. 



Estuary Trout. 



Leven Trout. 



Tweed Trout. 



1. 



1. 



1. 





1. 



£ in. nearly. 



s in. nearly. 



1*1. 





£ in. 



2. 



2. 



2. 





2. 



•571. 



•678. 



•664. 





•664. 



3. 



3. 



3. 





3. 



15 to 35 or 2-33. 



33 to 101 or 306. 



34 to 100 or 



294. 



32 to 95 or 306. 



The three great functions of respiration, locomotion and prehension, 

 as represented by the jaws, teeth and fins, may be held, as compared 

 with the general bulk of the body, to offer natural -history characters 

 more or less indicative of the natural state of the individual, and of con- 

 sequence of the species and subfamily to which it may belong: accord- 

 ingly it appeared on measurement, that, in respect of the fins gene- 

 rally, the true salmon was much more delicately organised than the 

 salmon trout, a coarser and no doubt a more rapacious fish, and that 

 assuming the head (the gill covers and branchial orifices included) 

 as a tolerably correct measure of the comparative strength of the gills 

 and jaws, or, in other words, of the organs of respiration and prehen- 

 sion, the salmon trout, or forelle, uniformly exceeded the salmon in 

 all such measurements. This law of proportions I found to hold 

 good in all the species of the Salmo Trutta I have yet examined ; 

 the coarse fish presenting enlarged proportions of the organs I have 

 just spoken of, as compared with the more delicate species; the com- 

 mon river trout, for example, of the brooks and rivers of Scotland, 

 compared with the estuary trout, and more especially with the deli- 

 cate char-trout of Loch Leven. The very young of the salmon kind, 

 in its proportions, approaches more nearly the type of the common 

 river trout than any other : as it grows these proportions alter, but 

 even when of 4 or 5 inches in length its proportions are still peculiar, 

 resembling more in their character the type of the river trout than that 

 of the salmon, to which the specimen we know belongs. The mea- 

 surements were made on the young of salmon from the Tay, the Shin 

 and the Annan. 



Thus the young animal, at a certain stage of its growth, is the type 

 not of the species to which it belongs by hereditary descent, but 

 XIII. 2 L 



