IOO 



THE POPULAR SCIENCE MONTHLY 



pods (1858-81): of this period is to 

 be mentioned his beautiful monograph 

 on the pantopods. In 1875 appeared 

 his paper " On the Origin of the Verte- 

 brata and on the Principle of the 

 Change of Function " ; it was a small 

 brochure, but it touched with a mas- 

 ter's hand some of the great problems 

 of its day. This paper Brooks declared 

 should be read by every one of his 

 pupils before he would give him his 

 doctorate — this in spite of Brooks's 

 lack of sympathy with the tenets which 

 Dohrn had laid down. It was this 

 paper which paved his way for re- 

 searches which were to extend over a 

 third of a century. And one may fol- 

 low the development of the subject — 

 and of Dohrn himself — in a series of 

 twenty-five voluminous memoirs. 



It was the " momentous problem of 

 the beginnings of the back-boned ani- 

 mals " which Dohrn sought to solve. 

 And upon this matter his writings are 

 encyclopedic. Vertebrates were to him 

 descendants of chaetopod worms; their 

 typical organs did not arise de novo 

 but as transformations of organs hav- 

 ing a different function ; animals of 

 simple structures were not as often 



primitive as Haeckel, for example, 

 would teach, but were frequently de- 

 , generate ; Amphioxus and Ascidians 

 were not in the line of descent of the 

 higher vertebrates, nor were lampreys 

 — the latter were rather degenerate 

 bony-fishes. In his early papers his 

 readers are carried along on the crest 

 of a splendid wave of enthusiasm. 

 " The problem is solved, ... all but 

 solved, . . . soon to be solved." But 

 this stage of conviction comes to pass 

 darkly into the background, new diffi- 

 culties keep appearing, and in later 

 papers one hardly realizes the genetic 

 bearing of the data which Dohrn is 

 bringing together. The method of the 

 paper of 1875, which was essentially 

 deductive, gradually gave place to an 

 elaborate inductive method; separate 

 organs of the vertebrata are studied 

 in turn, especially in the head region, 

 and the difficulties are traced gradually 

 into finer and finer ramifications, until 

 in the end he deals with what appears 

 to be purely the puzzle of nerve his- 

 togenesis. For Dohrn would not admit 

 that the head problem in the vertebrate 

 was not to be solved with the present 

 materials or by the aid of the embryo- 



The Naples Zoological Station. 



