342 On Certain Bacteria from the Air of New York City. 



more often of ditferent species, the commonest class being the 

 very short forms, " Microbacilli." No Spirilla were found. 

 Twent3"-four Micrococci and forty-four Bacilli were found in the 

 air, and of these the following nine Micrococci and nine Bacilli 

 occurred more than once : 



Micrococcus concentricus^ Zimm. Bacillus fascus, Zimm. 

 Micrococcus cremoides, Zimm. Bacillus finitimus ruber, Dyar. 

 Micrococcus cremoides albus, Bacillus decolorans major ^ 



Dyar. D3'ar. 



Micrococcus pyogenes aureus, Bacillus candicans, Frankland. 



Passet. Bacillus inutilis, Dyar. 



Sarcina flava, DeBar}-. Bacillus Hudsonii, Dyar. 



Micrococcus mobilis, Manrea. Bacillus mesentericus vulgatus, 

 Merismopedia rosea, Bumm. Fliigge. 



Micrococcus tetragenus vividus, Bacillus lactis erythrogenes, 



Dyar. Hueppe. 



Micrococcus tetragenus versati- Bacillus helvolus, Zimm. 



lis. Stern. 



Systematic Account. * 



I will proceed to detail the morphological and biological charac- 

 ters of all the species which I have w^orked out in the course of 

 this investigation. * I have prepared synoptic tables, so that all of 

 these species can be readil}^ and quickly identified. The composi- 

 tion of all the media of cultivation made us.e of is given at the 

 end of the systematic account. As far as possible, previously 

 used media have been employed, and the most often used of these 

 have been given prominence (though they do not always deserve 

 it from the "[loint of view of reliability) in oi'der to bring in line 

 the work already recorded by others in description of species. 

 My work has mainly consisted in the general application of a 

 series of tests uniforml}' to a rather large group of species, and 

 the result in the manner of their separation seems, on the whole 

 satisfactory' . If this work could be extended to cover all the 

 species of Bacteria, I think the operation of identifying species 

 would be far less confusing than it is at present. An objection 

 which I have not been able to overcome is the great length of 



* This includes all those jilanted for comparison as wfll as those derived 

 from the air. 



