Vol. 7, 1921 
ZOOLOGY: L. L. WOODRUFF 
41 
It will be evident from the foregoing outline that the vascular structures 
of the seedling are not constant but are highly variable, even within genet- 
ically very homogenous material. It is quite possible, therefore, that 
anatomical investigations based on but a few sections for each species 
might lead to erroneous results. Seedlings differing in external form are 
differentiated in their internal anatomy. Such differentiation is evident 
not only in mean number of bundles but in the degree of variability in 
bundle number. Thus, in normal seedlings the variability is higher in the 
hypocotyl than in the epicotyl, whereas in seedlings with three cotyledons 
and three primordial leaves just the reverse is true. The external form 
and the internal structure of the seedling are highly but not perfectly 
correlated. Finally in both normal and variant seedlings, the number of 
vascular elements of the several regions of the seedling are correlated in 
very different degrees ; the correlation between some is high ; between others 
it is practically wanting. 
Papers to appear in the American Journal of Botany may be consulted 
for details. 
1 The values given in each case are the maximum and minimum constants for the 
lines investigated. For the trimerous and dimerous seedlings all the averages are 
based on five lines. For the hemitrimerous seedlings the averages for primary double 
bundles and intercalary bundles are based on five lines while for the mid-region of 
hypocotyl and the mid-region of epicotyl they are based on six lines. Data for number 
of root poles are available for only three lines. 
2 Because of the extreme rarity of hemitrimerous seedlings it is not feasible to dis- 
cuss variability of bundle number in this group. 
THE PRESENT STATUS OF THE LONG-CONTINUED PEDIGREE 
CULTURE OF PARAMECIUM AURELIA AT YALE 
UNIVERSITY 
By Lorandk Loss Woodruff 
Osborn Zoological Laboratory, Yale University 
Communicated by R. G. Harrison, December 30, 1920 
As a matter of record it seems advisable to bring up to date and sum- 
marize the chief results derived from the writer's main pedigree culture 
of Paramecium aurelia. 
This culture, designated Culture I, was started on May 1, 1907, by the 
isolation of a "wild" individual which was found in a laboratory aquarium. 1 
The original specimen was placed in about five drops of culture fluid on a 
glass slide having a central ground concavity, and when this animal had 
produced four individuals, each of these was isolated on a separate slide 
to form the four lines of the culture. The four lines have not been kept 
distinct from one another throughout the work, but have been replenished 
by cells from one of the sister lines when, through accident or otherwise, 
one or another of the lines has become extinct. 
