14 FISHES OF AUSTRALIA. 



scales longitudinally, along the body from behind the 

 opercle (operculum) to the root of the caudal fin, and 

 even sometimes extending right out on to that appendage 

 itself. This is the so-called lateral line. Where it 

 exists, as in the more typical groups, it is deserving of 

 considerable attention. The scales of which it is formed, 

 are always of a construction different to those on the 

 rest of the body ; being perforated in the middle, to allow 

 of the free issue of the slimy, mucous substance which 

 is distributed so plentifully all over the body. Sometimes, 

 as in some of the fishes of the Yellowtail family and 

 others, the scales of the lateral line are raised and crested, 

 while in others, they are developed into spines or prickles. 



Many fishes (such as Catfishes, Goatfishes, etc.) are 

 provided with fleshy barbels or "feelers" in the vicinity 

 of the mouth; and, where these are present, they may 

 be taken generally as a sign that the fish is a "bottom" 

 feeder, the barbels being organs of touch (tactile organs). 



In fishes, we often find a most wonderful adaptation 

 in shape and colour to suit environment ; and the form of 

 the snout is particularly liable to modification, according 

 to the habits of life of a particular species. The 

 accompanying illustration of the snouts of a number of 

 our common fishes, will serve to emphasise this state- 

 ment. 



Sometimes, in addition to a fish possessing a protec- 

 tive colouration, it has irregular, skinny appendages, 

 which simulate seaweed, to a greater or lesser extent. 

 This is shown to some extent in the Red Rock-Cod, and 

 is very highly-developed in the Leafy Sea-horse. 



Colouration in Fishes : "Contrary to popular 

 opinion," says Bridge, "it may be doubted if any animals, 

 even Insects or Birds, can vie with living Fishes in the 

 brilliancy and changeability of their colours. The nature 

 of their habitat, the rapid fading of the natural tints after 

 death and the fact that museum specimens, however care- 

 fully preserved, afford but a ghostly resemblance to the 

 colours of the living animal, account, no doubt, for much 

 of the prevalent ignorance of the extraordinary extent to 

 which colour-development may proceed in a considerable 



