PREFACE. 



IN issuing the first part of the present work in a second 

 edition, and in bringing out the second, the Author has 

 little to add to what he has already said. 



The chief point upon which it may be desirable to 

 say a few words is, as to the object aimed at in the 

 Introductory portion of the work. The Introduction is 

 intended to exhibit to the student, in as brief a form as 

 possible, the leading principles of Zoological Science. 

 These principles are of the highest importance, and 

 no adequate knowledge of Zoology can be attained 

 without their full comprehension. At the same time, 

 the principles in question depend, in many cases, upon 

 data which are only evolved during the s-< stematic 

 study of the subject. For this reason, it is not to be 

 expected that the student should find himself fully 

 able to comprehend the Introductory portion of the 

 work, whilst still standing at the threshold of the 

 subject. Whilst the student, therefore, will do well to 

 glance over the Introduction before commencing the 

 study of the systematic portion of the work, he must 

 be prepared to find many points which he can only 



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