308 



SCIENCE 



[N. S. Vol. XLII. No. 1079 



LymnEeids by the characters of the shell, genitalia 

 (shape of prostate, relative size and form of the 

 penis and penis-sac) and radula. " 



On a basis of these criteria he has split the 

 genus Lymnwa, as defined by Haldeman, 1840, 

 Gould, Binney, 1868; Call, 1871; Tryon, 1872 and 

 1884, and more recently by Dall in 1905, into six 

 genera: Lymnwa, Pseudosuccinea, Badix, Bulim- 

 nwa, Acella and Galba. He has done this mainly 

 by raising a number of subgenera and sections of 

 former authors to generic rank. I wish to ask this 

 question: Is this at the present time justifiable? 

 (1) Baker lists 103 species and varieties of the 

 old Lymnwa in this work. Of but 33 have any- 

 thing of the anatomy, radula and genital organs 

 been studied. Therefore the shell characteristics 

 are the important ones after all. (2) All these new 

 genera are based largely on quantitative charac- 

 ters. The only qualitative character mentioned is 

 the radula and this is given quite a subordinate 

 place in the classification. (3) In his diagnosis of 

 the genus Galha in his key he states that the 

 "Penis" (epiphallus) is shorter than the "penis- 

 sac" (penis). However, for two of the species of 

 this genus the epiphallus is longer than the penis. 

 (See Baker, pp. 263 and 277.) 



In the mind of the writer our present knowledge 

 will not allow us to make a comprehensive classifi- 

 cation of the LymnEeids based on the anatomy of 

 the snail. We know too few species well. On the 

 other hand, the shell characters alone in a moUusk 

 with such a generalized form of shell as have the 

 Lymuffiids are not characters on which one can base 

 much reliance. On account of these reasons the 

 writer would make the recommendation that the 

 old genus Lymnwa should be retained in the sense 

 that it has been used for the past seventy years. 



In the Nautilus for June, 1915, Mr. F. C. 

 Baker answered the writer in an article en- 

 titled " On the Classification of Lymnseids."' 

 I think this may be taken as the typical atti- 

 tude of a taxonomist. He said: 



The writer can by no means agree with the state- 

 ment made twice in this paper (loc. cit.) that 

 generic names should not be added unless based on 

 undebatable grounds, because of the inconvenience 

 of the cataloguer. If this criticism should be rec- 

 ognized we should revert to the use of many of the 

 older names in the Pulmonata as well as in the 

 Naides. 



It is recognized, of course, that generic subdi- 

 visions can be overdone, but in the advancement of 



science the convenience of the cataloguer or teacher 

 is not considered. 



We welcome all additions to knowledge and we 

 know full well that the work of yesterday is ren- 

 dered obsolete by the work of to-morrow, but the 

 writer can not see how the reduction to subgenera 

 and sections of the names used as genera and sub- 

 genera in the monograph in question advances our 

 knowledge of the family any more than the raising 

 of a number of subgenera and sections to generic 

 rank, as Colton believes the writer to have done in 

 his monograph. This rather resembles a game of 

 see-saw. 



This whole discussion hangs on the ques- 

 tion, is it necessary to change generic names 

 to advance our knowledge? The writer be- 

 lieves that to change generic names without 

 an overwhelming amount of evidence in favor 

 of the change is hindering instead of advanc- 

 ing science. Species and minor groups, on 

 the other hand, can not be too much subdi- 

 vided. It is an advance to describe every vari- 

 ation that can he distinguished. Of this work 

 Bateson^ says : 



They will serve science best by giving names 

 freely and by describing everything to which their 

 successors may possibly want to refer, and gener- 

 ally by subdividing their material into as many 

 species as they can induce any responsible society 

 or journal to publish. 



In conclusion, generic names are those by 

 which animals are catalogued, therefore 

 should not be changed without overwhelming 

 evidence in favor of the change. This value 

 of the generic name has not been sufficiently 

 emphasized. 



Harold S. Colton 

 Zoological Laboratory, 

 University op Pennsylvania 



THE END OF CORy's SHEARWATER 



Cory's shearwater (Puffinus horealis) does 

 not exist. It seems a pity to abolish so time- 

 honored and respected a species; but the truth 

 is that it already stands abolished, and nothing 

 is required but the awakening of us American 

 bird-men to the fact. It is indeed a token of 

 provincialism on our parts that this remark- 

 able error should have gone for thirty-four 



2 ' ' Problems of Genetics, ' ' p. 249. 



