II. AMPHIOXUS AND THE ANCESTRY 

 OF THE VERTEBRATES. 



BY 



ARTHUR WILLEY, B.Sc. Lond., 



Tutor in Biology, Columbia UniversiUj ; Balfour Student of the 

 Unirersity of Cambridge. 



8vo. Cloth. $2.50, net. 



The purpose of this vohime is to consider the problem of the 

 ancestry of the Vertebrates fi-om the standpoint of the anat- 

 omy ixnd development of Amphioxns and other members of the 

 group Protochordata. The work opens with an Introduction, 

 in which is given a brief historical sketch of the speculations 

 of the celebrated anatomists and embryologists, from Etienne 

 Geotfroy St. Hihiire down to our own day, upon this problem. 

 The remainder of the first and the whole of the second chapter 

 is devoted to a detailed account of the anatomy of Am])hioxus 

 as compared with that of higher Vertebrates. The third chapter 

 deals with the embryonic and larval development of Amphioxns, 

 while the fourth deal.'* more briefly with the anatomy, embryology, 

 and relatioushijts of the Ascidians; then the other allied forms, 

 Balanoglossus, (Jephalodiscus, are described. 



The work concludes with a series of discussions touch- 

 ing the problem jiroposed in the Introduction, in which it is 

 attempted to define certain general principles of Evolution by 

 which the descent of the Vertebrates from Invertebrate ancestors 

 may be supposed to have taken place. 



The work contains an extensive bibliograph}^, full notes, and 

 135 illustrations. 



TABLE OF CONTENTS. 



Introduction. 



Chapter I. Anatomy of Amphioxus. 

 II. Ditto. 



III. Development of x'Vmphioxus. 



IV. The Ascidians. 



V. The Protochordata in their Relation to 

 THE Problem of Vertebr.\te Descent. 



