OF WASHINGTON. 59 



Mr. Ashmead, apropos to the generic position, said that in his 

 opinion, instead of enlarging the characters of Ptomaphagus to 

 include this species, he would prefer the erection of a new genus 

 as the simplest course and the least confusing to subsequent 

 workers. Mr. Schwarz differed from the speaker and said that 

 in many cases it was unquestionably necessary to enlarge the 

 scope of a genus on the discovery of new forms. To reduce 

 the case to an absurdity, he mentioned the erection of two genera, 

 Eutyphlus LeConte and Nicotheus Casey, which afterwards 

 were proved to be different sexes of the same species. That 

 was a case, he said, where the generic characters unquestionably 

 had to be enlarged. Dr. Gill said that the point raised led at 

 once into a discussion of very broad scope and involved questions 

 as to what genera really are and what characters are to be used 

 for genera. He stated that the fact of great diversity in the 

 sexes may itself be used as a generic character. The mere fact 

 of cecity, in his opinion, is not valuable as a generic character, 

 and he very much doubted the expediency of using such a physi 

 ological character, since some species have a tendency to become 

 blind under certain circumstances. He referred tb a blind cat 

 fish which occurs in caves in Pennsylvania and which is very 

 closely allied to surface forms. Cope and formerly Jordan con 

 sidered this a distinct genus. He, however, always considered 

 it a true Amiurus, nearly related to the common A. melas, and 

 recently Dr. Jordan has changed his opinion and now agrees 

 with Dr. Gill. 



As to Hemimerus (mentioned by Mr. Cook), Dr. Gill ex 

 pressed himself as believing that it is undoubtedly the represen 

 tative of a very isolated family, but whether it should be given 

 higher rank depends upon the determination of the actual char 

 acters and upon the value which should be given to such charac 

 ters. The first point he illustrated by the fact that the interpre 

 tations of the mouth-parts made originally by Saussure have 

 been attacked by Hansen. 



Mr. Schwarz, as illustrating the rapidity with which surface 

 forms may assume cave-inhabiting characteristics, mentioned the 

 case recently described in the Bulletin of the Museum of Natural 

 History, of Paris, in which a Trechus found in the catacombs of 



