248 A Biometrical Study of Conjugation in Parameciwn 
These tables show very clearly the relation of the different characters in the 
different series. It will be noted that with a given change in either length or 
breadth roughly about twice as great a probable change in the associated character 
(breadth or length) occurs in the non-conjugants as in the conjugants. This is 
primarily the result of the higher correlation between length and breadth in 
the non-conjugants. On the other hand the index changes less with a given 
change in length or breadth in the non-conjugants than in the conjugants. This 
means that the shape as measured by the index is more constant with changing 
lengths and breadths in non-conjugants than in conjugants. In all cases, as we 
should expect, a unit change in breadth makes a larger change in the index than 
a unit change in length. 
We may now summarize the results of this section as follows. It has been 
found that in several samples taken at different times from two different cultures 
there is a pronounced differentiation between conjugant and non-conjugant 
Paramecia living in the same culture at the same time, in respect to type, 
variability and organic correlation. The conjugant individuals when compared 
with the non-conjugant are found to he shorter and narrower, and less variable in 
both length and breadth. The conjugants have a lower mean index, or in other words 
are relatively more slender, and are more variable in shape of body as indicated 
both by the lengtJi -breadth index and by the organic correlation between length and 
breadth. Tlie conjugants have the length and breadth less Jiighly correlated than the 
non-conjugants. I would especially emphasize the fact that the differences here 
enumerated are by no means small and of doubtful character, but are, on the 
contrary, of large and significant amount. The difference in size between con- 
jugants and non-conjugants is perfectly obvious to the eye without any measuring, 
if one's attention is only called to the matter. The differences here are quite as 
great or even greater than those which distinguish the most divergent races of 
men, for example, in the character stature. This point is dwelt upon lest someone 
might hastily conclude that the differentiation found between conjugants and 
non-conjugants was something dependent on the proper kind of figure-juggling. 
The discussion of the biological significance of this differentiation will be left to a 
later section of the paper, where all the results may be taken as a whole. 
During a period in the history of a single culture, occupying about four weeks 
in time, definite and significant changes occurred in the type of the non-conjugant 
Paramecia. Similar changes occurred in the conjugants but were smaller in 
amount. Up to within a week of the dying out of the Paramecia the individuals 
became, as time went on, longer, without a corresponding increase in breadth. As 
a consequence the body became relatively slenderer in shape. The relative varia- 
bility of the characters remained constant throughout this period. During the 
last week of the cultural history the individuals became broader again. 
