74 THE ZOOLOGIST. 



Keferring to the visual organs of fish Dr. Hamilton says : — 



M It would be interesting to determine at what angle fish perceive objects 

 behind them, or directly in front of them. It would appear in many that 

 the vision is chiefly directed upwards and laterally, but how far their vision 

 (particularly in fish which get their food chiefly on the surface of the 

 water) extends backwards and forwards is not yet determined. An object 

 placed laterally, or above, will almost immediately attract or scare. We 

 have many times been able to get close to a Trout by approaching it directly 

 from behind, when the slightest deviation laterally would send him away. 

 In approaching fish, not sufficient consideration is given to the powers of 

 refraction and the medium through which a fish sees ; and it should be 

 remembered that fish do not see objects as we see them "(p. 183). 



The distinctions between the young or parr stage of the 

 Salmon (Salmo salar), the Sea Trout (S. trutta), and the Kiver 

 Trout {S.fario), are thus summarised by our author : — 



" In the Salmon parr the body is long and graceful ; the head and snout 

 longer; the parr marks (transverse dark bands) very distinct and separated 

 by broad intervals ; the pectoral fins narrow, and with the ventral and anal of 

 a dusky hue ; the tail much forked. 



" In the migratory Trout the body is thick and short ; the head and 

 snout more rounded ; the dorsal fin often spotted ; the pectoral broad, and 

 with the ventral and anal orange coloured ; the adipose fin tinged at the 

 end a light orange ; the tail but little forked. 



" In the river or brook Trout the body is long and not so shapely ; 

 the head short ; the snout very obtuse ; the eye large ; the dorsal fin 

 spotted ; the adipose fin with a scarlet red tip ; the tail square, and but 

 little forked. 



" To the experienced, and even to some experts, the absolute certainty 

 of the distinction is often a matter of difficulty." 



An interesting chapter is that on Eels (pp. 286—291), wherein 

 the author discusses the species, migrations, and propagation of 

 these fish, and the distinguishing characters of the sexes. Most 

 writers on Eels have stated that they breed only in the brackish 

 water of the estuaries of our rivers, but many good observers 

 declare that some Eels do breed in fresh water, in ponds and 

 lakes which have no connection with rivers that run to the sea. 

 Dr. Hamilton does not inform us to which of these two views he 

 is inclined, nor does he explain, if Eels do not breed in isolated 

 lakes and ponds, how it is that the supply of these fish is main- 

 tained there. Many places might be named where from time 

 immemorial fine large Eels have been taken when required for 



