94 STORRS AGRICULTURAL EXPERIMENT STATION. 
except the original description made several years ago, a de- 
scription which may be too incomplete to be of very much value. 
These are in a few cases retained in the following pages, but 
only for species that possess very striking characteristics. For 
instance, MZ. 1. rubzdus, having the power of producing a bril- 
liant red pigment, is so striking a type that we did not think 
it wise to omit it even though the description was based upon 
a single culture obtained several years ago and is more or less 
. incomplete. 
It will manifestly require many years before a complete 
knowledge of dairy bacteria can be obtained. While we have 
in the following pages described about one hundred and sixty 
types, we recognize that this is by no means the complete list 
of even common forms; but to complete the list will require 
many years of laborious study. When we recognize the extreme 
variability of bacteria types, especially in physiological charac- 
ters upon which their classification may be partly based, it be- 
comes evident that to reach an end of the description of dairy 
forms is almost an impossibility. Our recognized types, as will 
be shown, vary in all directions and run into each other by more 
or less complete intermediate links. Every new set of cultures 
which we obtain from even similar sources show variations in 
various properties connecting them more or less with other 
types. This has been forced upon us more and more, as the 
data we have collected has increased, until we have almost con- 
cluded that the task of arranging these forms into species or 
even groups is hopeless; for even at the very best these groups 
will show such wide internal variations as to connect them 
more or less completely with the closely associated forms. 
Before such groupings can be finally made an immense amount 
of work and many years’ study must be given. But every 
attempt to formulate our ideas clears our conceptions, and 
hence it is thought that the present endeavor to arrange the 
dairy bacteria in a scheme of classification, even though of 
necessity incomplete and doubtless requiring later changes, 
will bring us nearer to a proper conception of their relation and 
help toward a real understanding of problems of bacteriology. 
The question of species —The question of species among bac- 
teria is at present an insoluble puzzle. It has become manifest 
that it is quite impossible to carry over to the classification of 
