PREFACE TO THE SECOND EDITION. 



The favourable reception granted to the first edition of this 

 book has already led to a demand for a second. In pre- 

 paring this, I have endeavoured to take advantage of the 

 suggestions of kindly critics. The book is intended to serve 

 as a manual which students of Zoology may use in the 

 lecture-room, museum, and laboratory, and as an accom- 

 paniment to several well-known works, cited in the 

 Appendix, most of which follow other modes of treatment. 



To numerous authorities I acknowledge an obvious 

 indebtedness, a detailed recognition of which would be 

 out of place in a book of this kind. But I must thank 

 Dr. Ramsay Traquair for helping me with the chapter on 

 Fishes, Dr. Beard for revising the pages on the general 

 structure of Vertebrates, and Dr. Gilchrist for suggestions 

 as to the chapter on Molluscs. For the imperfections in 

 these chapters I am, of course, alone responsible. 



In preparing this revised edition I have been assisted 

 throughout by Miss Marion Newbigin, B.Sc. She has 



