Vol. 7, 1921 
GENETICS: W. II. TALIAFERRO 
141 
value by the 25th day. At first it looks as if the mean tends to rise even 
until the 32nd day. That this is not the case, however, is shown by the 
fact that the value on the 25th day does not vary appreciably from that 
of the 72nd day. 
The same type of result was obtained for all of the six distances shown 
in figure 1, namely, for the distances posterior end to parabasal body, 
parabasal body to nucleus, nucleus to anterior end, anterior end to end of 
t 
1 
LiJ 
o 
13- 
O 
w 
I 
p~ 
o 
p- 
P- 
3 
Cr> 
C 
+-• 
Q 
3 
«C3 
fWidrh 
... A 
•Post-Para 
Papa- 
-Nuc 
Nuc -Ant 
Ant-End 
— V 
T Length 
FIG. 1 
Diagram of T. lewisi showing the parts of the organism and the distances measured 
in this work. The parts of the organism are placed vertically while the dis- 
tances are placed horizontally. The latter consist of the distance from 
(1) posterior end to parabasal body, (2) parabasal body to nucleus, 
(3) nucleus to anterior end, (4) anterior end to end of 
flagellum, (5) total length, and (6) width. 
flagellum, and width, although most of the constants do not reach as low 
a level as is the case with those for total length (see table 1). Curves of 
this nature were obtained in four rats. These results prove, what we had 
been led to believe from cytological evidence, viz., that there is practi- 
cally no division or growth in T. lewisi after the 25th day of the blood 
infection. 
After it was determined that there was no significant change in the 
mean or coefficient of variation after the 25th day we decided to make 
all measurements after this day. Most of the measurements which will 
be given in a later report were made on the 30th day of the blood infection. 
The fact that the trypanosomes in the blood of the rat reach what we 
can consider an adult stage makes size a very favorable character with 
