8ALPA IN RELATION TO EVOLUTION OF LIFE. 183 



While it is not my purpose to discuss the ancestral history of the 

 vertebrates, the remote phylogeny of the tunicates is unquestionably 

 identical with that of the other chordata, and I cannot ignore the 

 general acceptance of an opinion which is absolutely irreconcilable 

 with the one which I have presented. 



This prevailing opinion has interwoven itself with the literature 

 in such a complicated way that one may well shrink from the in- 

 terminable labor which the critical revision of the whole of it would 

 involve. I myself decline to undertake what I regard as an un- 

 profitable and useless task ; unprofitable, as the literature rests on 

 an untenable and false basis, and useless, since I do not hope to 

 induce those who have stored their minds with the endless details 

 of morphology docketed and pigeon-holed according to a false 

 system, to unload all this rubbish and to build again on a new 

 foundation. 



I shall therefore restrict myself to a discussion of the origin of 

 the two most characteristic systems of tunicata organs, the gill-slits, 

 and the pharyngeal ciliated cells and gland cells ; and I shall here 

 confine myself to the observations and reflections of a single writer, 

 Dr. Dohrn. 



I make this selection the more willingly, as Dohrn's name is 

 most intimately associated with the annelidian hypothesis, and 

 because his writings are not only the ones which have been most 

 influential, but also the ones which are most comprehensive and 

 most attractive to the reader. 



The " Ursprung der Wirbelthiere " is a most fascinating book. 

 Soon after it appeared I placed it in the list of works which my 

 students are advised to read, and for many years an acquaintance 

 with it has been expected of all who have been examined for the 

 degree of Ph. D. in the Johns Hopkins University. 



My students have even prepared for their own use an English 

 translation of it, and I have read it with them several times with 

 interest and pleasure. At the first reading my pleasure was almost 

 that of conviction, but as the ingenious details became familiar, 

 and the essay was more sharply focused in its completeness, and 

 was held, as it were, at arm's length, so that the whole picture 

 could be seen at one view, I have read it, as I have read Gulliver's 

 Travels, with admiration for the skill which has elaborated it in 



