*v* 



PREFACE 



The twelfth edition of Borradaile, the first major revision since 

 the book was pubhshed forty-five years ago, has on th(.' whole 

 been well received both by reviewers and by readers. Complaint 

 was commonly made of the illustrations, both old and new, and 

 with some justification. The necessity for a new edition less than 

 two years after the edition was published has allowed the replace- 

 ment of some forty-three of these, and I hope that in future 

 editions more will be treated in the same way. I am grateful to 

 all those who have pointed out misprints or lapsus calami, all of 

 which have been corrected. I thank also those who have reported 

 errors; if a reviewer finds that any of these remain uncorrected 

 it is because, after consulting the best authorities available to me 

 (including, in two instances, the animal itself) I have come to the 

 conclusion that what I originally wrote was nearer to the truth. 

 I have also tried to remove a few ambiguities, and statements 

 throughout the book have been corrected to accord with new 

 knowledge. 



The interest that the book has aroused is very pleasing, but 

 there is one respect in which I cannot agree with some of my 

 critics, who would have liked to see the old morphological basis 

 entirely abandoned. While I agree completely with them on the 

 importance of physiology and ecology, I believe that there is 

 still good reason for not trying to force on students a fusion of 

 the morphological, physiological and ecological aspects of the 

 subject, which, at the level for which this book is written, few of 

 them will understand. I have retained the type-system not, as 

 one reviewer said, because I have never known any other, but 

 because I have seen, as a teacher, as an examiner, and as an 

 attender at scientific meetings, the bad results of attempts to be 

 'synthetic' or 'comparative' before the student knows the basic 

 facts of morphology. They simply do not work. The sections in 

 this book on parasitism (now put as a separate chapter) and on 

 the coelomate body, and those on vertebrates at the end, read after 

 those on the relevant types, will give the student of sixteen to 

 nineteen or so, enough on which to exercise his mind (I hope he 

 will do so critically). I originally intended to include a general 



