PREFACE. vii 



intelligible as possible. I trust my readers will not be 

 disappointed with the results. The sources from which 

 the woodcuts are taken have been in all cases acknow- 

 ledged, and in the. cases where no source is given the 

 illustrations are my own. 



I take this opportunity of acknowledging my great 

 obligations to Professors Agassiz, Huxley, Gegenbaur, 

 Lankester, Turner, Kolliker, and Claus, to Sir John 

 Lubbock, Mr Moseley, and Mr P. H. Carpenter, for the 

 use of electrotypes of woodcuts from their works. 



I am also under great obligations to numerous friends 

 who have helped me in various ways in the course of my 

 labour. Professor Kleinenberg, of Messina, has read 

 through the whole of the proofs, and has made numerous 

 valuable criticisms. My friend and former pupil, Mr 

 Adam Sedgwick, has been of the greatest assistance to 

 me in correcting the proofs. I have had the benefit of 

 many useful suggestions by Professor Lankester es- 

 pecially in the chapter on the Mollusca, and Mr P. H. 

 Carpenter has kindly revised the chapter on the Echino- 

 dermata. 



I am also much indebted to Dr Michael Foster, Mr 

 Moseley, and Mr Dew-Smith for aid and advice. 



