vi PREFACE. 



The brevity of the descriptions is, however, to some extent 

 made up for by the number of woodcuts. Most of these are 

 taken from the German edition, but several new figures have 

 been added. 



The arrangement of the book according to organs, and not 

 according to groups of animals, is likely to render it more difficult 

 for a beginner, and a general knowledge of zoology will be of 

 great assistance. The pages on which the different groups are 

 described are, however, collected together in the index, so that the 

 sections relating to any one group can be easily referred to. The 

 present arrangement seems to be the only possible one if the book 

 is to be founded on a scientific basis, for it is most important that 

 the student should grasp the fact that there has been an evolution 

 of organs, as well as of animals. 



The more theoretical and detailed matter is printed in small 

 type, and in the form of notes : the student should in most cases 

 pass this over when reading the book for the first time. A black 

 and a spaced type have been used to render prominent important 

 words or sentences. 



A bibliography is appended at the end of each chapter. This 

 in no case presumes to be anything like a complete list of the 

 literature of the subject : our object has been more particularly to 

 mention the recent and the more important works, though many of 

 these have doubtless been omitted. References to other researches 

 can be found by consulting the works mentioned. 



At Professor Wiedersheim's suggestion, I have not inserted a 

 translation of the preface to the original, as it seemed unnecessary 

 so to do. I may, however, mention that the book was written 

 for students of Medicine, as well as for those of Comparative 

 Anatomy: the intimate connection of the two subjects renders it 



