Vlll PREFACE. 



of learning, with as little trouble and doubt as 

 possible, the generic name of every animal that 

 has been recognised by naturalists as inhabiting 

 the British seas ; from the lowest Sponge, up to the 

 Whale. To this universality there are only these 

 exceptions : — 



1. That the Intestinal Worms (Entozoa) are not 

 included. Properly speaking, they are no more 

 marine, than they are terrestrial animals; for though 

 some of them live in marine animals, their proper 

 sphere is not the water or the land, but the living 

 tissues of other creatures ; they have a world of 

 their own. 



2. That the swarming millions of animalcules, 

 known as Infusoria, which the microscope reveals 

 in the sea, as well as in fresh water, I have not 

 included in detail ; for reasons which will be found 

 under the head of this Class. 



Knowing by experience the difficulties which 

 lie in the way of identifying animals by published 

 characters, I have laboured to remove, or to lessen 

 those difficulties as far as was possible. I have 

 endeavoured to make these pages practically useful 

 to the beginner, while yet they should be precise 

 enough to serve the advanced zoologist as a con- 

 venient medium of reference. Many of the dif- 

 ficulties in the path of science are not inseparable 

 from it ; the language used is often unnecessarily 

 technical, and yet, strange to say, loose withal 



