KENDALL: WHAT CHARACTERS DISTINGUISH SPECIES? 187 



measurements mentioned in these papers indicate an absorp- 

 tion of 2 to 3 per cent of the radiations emitted at 1000° C. 

 for the average humidity of Washington. 



Dr. H. H. Kimball, of the U. S. Weather Bureau, very kindly 

 sent me comparative data, showing that the vapor pressures at 

 Naples are considerably higher than at Washington. From these 

 data it would appear that the correction for atmospheric ab- 

 sorption must be at least i per cent. For the low temperatures 

 at which the radiator was operated, a fair estimate of the cor- 

 rection to the radiation data obtained by Kahanowicz is 1.5 

 to 2 per cent, or a value of o- = 5.69 to 5.72 X io~^^ watt cm~- 

 deg~^. In other words, the Naples value of the coefficient 

 of total radiation is comparable with other recent determinations 

 which indicate a value of o- = 5.7 X lo"^'^ watt cm~- deg~^ 



BIOLOGY. — What kind of characters distinguish a species from 

 its subdivisions?^ William C. Kendall, Bureau of Fisheries. 



I do not claim to be an authority on Taxonomy, although 

 I have labored to some extent in Systematic Ichthyology, which 

 for a long time was to me a game of "follow the leader," and in 

 which game, it may be said, I was a "bhnd" follower. 



The fixed views of my leaders, regarding what kind of char- 

 acters should constitute species and subspecies respectively, 

 seemed thoroughly reasonable and logical, but when independ- 

 ently I attempted to apply them in practice, I found myself 

 in a dense fog from which I have not yet emerged. 



Briefly stated, a species was such by virtue of possessing one 

 or more "distinct and constant" characters distinguishing it 

 from all other species. These characters might be pronounced 

 or shght, but if "constant'' entitled the form so characterized 

 to a binomial label. Of course if there was only one specimen, 

 which was commonly the case, the above specific condition 

 was fulfilled. 



If, however, two forms, which, if observed by themselves in 

 two separate localities, would seem to be distinct species, should 



1 Remarks at the Symposium at the meeting of the Biological Society, Saturday, 

 March 8, 1919- 



