QLS21 



-R46 



1397 



PEBFACE. 



IN the following pages the term skeleton is used in its 

 widest sense, so as to include exoskeletal or tegumentary 

 structures, as well as endoskeletal structures. It was thought 

 advisable to include some account of the skeleton of the 

 lowest Chordata animals which are not strictly vertebrates, 

 but it seemed undesirable to alter the title of the book in 

 consequence. 



The plan adopted in the treatment of each group has 

 been to give first an account of the general skeletal characters 

 of the group in question and of its several subdivisions ; 

 secondly to describe in detail the skeleton of one or more 

 selected types ; and thirdly to treat the skeleton as developed 

 in the group organ by organ. 



A beginner is advised to commence, not with the intro- 

 ductory chapter, but with the skeleton of the Dogfish, then 

 to pass to the skeletons of the Newt and Frog, and then 

 to that of the Dog. After that he might pass to the intro- 

 ductory chapter and work straight through the book. I have 

 endeavoured to make the account of each type skeleton 

 complete in itself; this has necessitated a certain amount of 



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