PREFACE vii 



already given in my brother's published works ; and, 

 in Part II, I have intentionally made use of these 

 descriptions, borrowing very freely from the Elementary 

 Biology, as well as (with Professor HaswelTs permission) 

 from the Textbook of Zoology ; and to a less extent, from 

 the Zootomy. 



The practical directions are mainly based on a series of 

 Laboratory-instructions I drew up some years ago for 

 the use of my junior classes, which consist principally 

 of students preparing for the Intermediate Science ex- 

 amination of the University of Wales, the Preliminary 

 Scientific examination of the London University, and the 

 first examination of the Conjoint Board of the Royal 

 Colleges of Surgeons and Physicians. The time such 

 students can devote to an elementary course in the sub- 

 ject is limited ; and throughout the book I have borne in 

 mind that the main object of teaching Zoology " as a 

 part of a liberal education is to familiarise the student 

 not so much with the facts as with the ideas of the 

 science," but at the same time that he should be pro- 

 vided with a sound basis of facts so arranged, selected, 

 and compared as to carry out this principle. 



Our original intention was to include one or more 

 examples of each of the larger phyla, and also to 

 add a practical exercise after each type, giving general 

 directions for the examination of an allied form for com- 

 parison. But I found that this would be impossible 

 within the space of a single volume, and it was therefore 

 necessary to limit the descriptions mainly to those 

 animals to which the students for whom the book is 

 chiefly intended have to give special attention. This 

 has resulted in rather a heavy balance on the side of 

 Vertebrates ; but on the whole, I think that if sufficient 

 work is done on the lower animals to illustrate certain 

 main facts and generalisations, a comparative studv of 



