8 BULLETIN 81, UNITED STATES NATIONAL MUSEUM. 



sentatives of the same species from any other part of the world. If 

 variants occur in one region they will, as far as we know, be repeated 

 in any locality where the determining conditions are found. 



As "insufficiently described" are listed species that can not be 

 definitely placed on the information at present available; the majority 

 of these are hopeless, but it is possible that some may still prove 

 valid. Wliile apparently very vague, a description may nevertheless 

 contain some clue that will enable us to identify the species when 

 it is found again. It would seem inadvisable, however, to revive old 

 and forgotten names unless there is some definite reason for domg 

 so; whUe new names should not be given to old species, it is almost 

 equally confusing to attach new animals to rejected names. 



The International Code of Zoological Nomenclature as it stands 

 to-day has been rigorously applied throughout, as offering the only 

 means of escape from the present chaotic condition. As a conse- 

 quence, a number of changes have been introduced which will no 

 doubt cause temporary inconvenience, but it is hoped the final 

 gain will compensate for this. For references to Schrank, Briefe an 

 Nau, I am indebted to Prof. Dr. Anton Collin, Berlin, and to Dr. 

 P. de Beauchamp, Paris, for reference to Lauterborn, Nordische 

 Plankton-Eotatorien. In all other cases the original descriptions 

 have been consulted unless otherwise noted in the text. 



No pains have been spared to make the work complete; still, in 

 dealing with a literature of such extent it is to be expected that 

 omissions may have occurred. 



A bibliographic list has been added, and as far as possible it has 

 been verified from the original publications. While many authors 

 give a list of the papers to which they refer, it is probably not unfair 

 to say that one-half of such references are either erroneous or incom- 

 plete, thus giving the reader endless trouble when he tries to verify 

 the statements. 



In this list is included a large amount of literature relating to dis- 

 tribution, morphology, technique, etc., without any attempt at 

 completeness, except for works bearing on nomenclature. Where 

 no library reference is given, the publication has not been consulted. 



This undertaking would have been impossible but for the assist- 

 ance of zoologists here in Washington and elsewhere. It is a pleasure 

 to express my gratitude for help and advice from Dr. Paul Bartsch, 

 Dr. Theodore Gill, Miss M. J. Rathbun, Dr. L. Stejneger, Dr. C. W. 

 Stiles, of the United States National Museum, Washington; Dr. 

 H. S. Jennings, Baltimore, Maryland; Dr. C. A. Kofoid, Berkeley, 

 California; Dr. P. de Beauchamp, Paris; Dr. Anton Collin, Berlin; 

 Dr. E. F. Weber, Geneva; Dr. A. Behning, Saratov; Dr. N. V. 

 Voronkov, Moscow; and Dr. S. A. Zernov, Sevastopol. 



