PREFACE. ix 



necting link between Protochordate and Chordate organ- 

 isation. Before entering into any of these discussions, 

 the author has given a thorough systematic and structural 

 treatment, especially of Amphioxus. 



This exquisite form, Amphioxus, is of almost world-wide 

 distribution and has enjoyed the attention of every great 

 zoologist for over half a century, yet the most recent 

 studies upon it have been among the most productive of 

 discovery. Its interest and value as an object of biologi- 

 cal education has steadily increased with the knowledge 

 that in contrast with all the related forms, it stands as 

 a persistent specialised but not degenerate type, perhaps 

 not far from the true ancestral line of the Vertebrates. 



H. F. O. 



