EVOLUTION OP ORGANS IN THE CHORDATA. 265 



Dr. Dohrn's Inquiries into the Evolution of 

 Organs in the Chordata. 



By 



«r. T. Cunningham, B.A., F.R.S.E. 



Seven years elapsed from the publication of the ' Ursprung 

 der Wirbelthiere ' before the appearance of the first of Dohrn's 

 ' Studien zur Urgeschichte des Wirbelthierkorpes/ that on 

 the mouth of Teleosteans. As he points out in a short preface 

 to that paper the three chief peculiar articles of faith in his 

 previous essay, in comparison with the views current at the 

 time, were that the ancestors of Vertebrates closely resembled 

 Annelids, that the principle of change of function was the 

 safest guide in tracing morphological histories, and that the 

 extent to which degeneration might proceed was unlimited. 



In the attempt to reconstruct the Vertebrate ancestor, Dohrn 

 has concentrated his attention almost exclusively on the 

 actual structure and development of the organs of existing 

 Vertebrates, convinced that a great deal of what was generally 

 believed concerning the relation of the organs was inaccurate, 

 and that no light could be thrown on the question by hasty 

 conclusions drawn from superficial resemblances of the organs 

 of Vertebrate and other embryos, until the organisation of 

 the Vertebrates themselves was more thoroughly investigated. 



The following is a list of the studies with the dates of pub- 

 lication : 



1882. I. " Der Mund der Knochenfische." 



II. " Die Entstehung und Bedeutung der Hypophysis bei den 

 Teleostiern." 



1883. III. " Die Entstehung und Bedeutung der Hypophysis bei Petro. 



myzou Planeri." 



