CHAPTER XII 



VERTEBRATA 



Pisces. A definition of what constitutes a fish seems 

 rather superfluous, but for the sake of uniformity we must 

 render it. 



The text-books define the fishes as follows : 



Cold-blooded, aquatic animals, generally clothed with 

 scales ; swimming by means of fins ; breathing exclusively 

 by gills ; sexes separate, and reproduction by eggs, which 

 in a small number of species (e.g. sharks) hatch within 

 the parent. 



Treating of the fishes in a book which is intended to 

 apply simply to the animals of the shore that is, to those 

 that occur between tide limits presents some difficulties ; 

 for, while a great number of fishes are essentially shore - 

 haunting that is, breed between tide limits and spend 

 their lives in pools, or in situations that are accessible 

 when the tide is at lowest limit there are many others 

 which, when adult, live in deep water, but spend their 

 earlier lives inshore, notably the flat fishes. 



It will be well, therefore, to draw a more or less im- 

 perfect boundary line, and count as shore fishes bnly 

 those that are more frequently seen within tide limits 

 than beyond. 



We shall take them, also, not according to classes, but 

 approximately in the order in which they are most fre- 

 quently encountered by the shore collector or observer. 



On rocky coasts, or where these are loose stones inter- 



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