xii PREFACE 



and endless pains he has taken to produce the coloured 

 illustrations from original black and white photographs 

 supplied either by Mr. D. P. Wilson or taken specially in 

 the Plymouth laboratory ; for his care in producing the 

 wash and line drawings under our directions ; and for his 

 generous assistance and advice in all matters pertaining to 

 the arrangement of the illustrations. 



F. S. RUSSELL. 

 C. M. YONGE. 



