THE SIMPLE ASCIDIANS FROM THE NORTHEASTERN 

 PACIFIC IN THE COLLECTION OF THE UNITED STATES 

 NATIONAL MUSEUM. 



By William E. Ritter, 



Of the Scripps Institution for Biological Research. La Jolla, California. 



INTRODUCTION. 



Although the collection of Ascidians which is the subject of this 

 memoir is not of exceptional magnitude or interest, and although 

 much time and labor have been expended on it, yet I am aware that 

 much more study could have been profitably devoted to it. Par- 

 ticularly might the descriptions have been carried further in the 

 direction of the number of individuals examined for each species. 

 It is not at all impossible that had this been done the specific groups 

 recognized would have been different in several instances. Further- 

 more, I am convinced that the methods currently employed in sys- 

 tematic ascidiology, particularly for counting structures the charac- 

 teristics of which are given quantitatively, ought to be more refmed 

 and accurate than they are. Were our observational procedure to 

 be improved in the two respects mentioned, and were statistical 

 methods to be made more use of, I have no doubt that highly reward- 

 ing results over and above those now reached by systematic studies 

 would come forth; not only would the central aim of classificatory 

 research, namely, the delimitation and definition of groups, be made 

 more trustworthy, but various interests beyond those of classifica- 

 tion proper would be at least formulated. 



The value of systematic studies as a revealer of problems comes 

 from the circumstance that, bringing, as of necessity they do, before 

 the student large numbers of individuals and kinds of individuals 

 every one of which is different in some way from any of the others, 

 they inevitably raise questions almost as numerous and varied as the 

 organisms themselves. 



Looking upon systematic zoology in this way and so taking it for 

 granted that the collection now in hand will be worked over again in 

 the future by other zoologists employing more rigorous methods, I 

 have prepared, as far as possible in tabular form, considerable matter 

 not usually included in papers on systematic ascidiology. 



While much regretting that a larger number of dissections could 

 not be made and the data ascertained with greater accuracy, one con- 



Proceedings U. S. National Museum, Vol. 45— No. 1989. 



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