402 The Relation of Binary Fission to Variation 
TABLE I. 
Length, Breadth, and Breadth-Length Index in each member of 100 Pairs of 
Paramoecium caudatum, produced by asexual division. 
First Member 
Second Member 
First Member 
Second Member 
First Member 
Second Member 
_ 
CD 
'S) 
C 
X 
OJ 
"So 
rr-t 
X 
X 
X 
Qj 
a 
CD 
X 
0) 
a 
n 
Breac 
a 
Breac 
CO 
CP 
cu 
00 
a 
Breac 
a 
CD 
1-1 
a 
O) 
h^l 
m 
« 
cu 
m 
a 
265 
65 
•245 
245 
60 
— 
■245 . 
225 
65 
•289 
220 
65 
■295 
245 
75 
•306 
235 
85 
•362 
280 
65 
•232 
275 
55 
■200 
215 
70 
■326 
210 
70 
■333 
235 
75 
•319 
230 
70 
•304 
250 
45 
■180 
230 
50 
■217 
230 
70 
■304 
210 
90 
■429 
230 
80 
•348 
220 
70 
•318 
270 
60 
•222 
250 
70 
•280 
220 
80 
■364 
210 
85 
■405 
205 
85 
•415 
200 
85 
•425 
285 
85 
•298 
280 
85 
■304 
225 
55 
■244 
215 
60 
■279 
230 
65 
•283 
230 
60 
■261 
255 
70 
•275 
250 
75 
■300 
215 
65 
■302 
200 
70 
■350 
255 
75 
•294 
250 
75 
■300 
185 
70 
•378 
180 
65 
■361 
200 
75 
■375 
200 
75 
■375 
250 
70 
•280 
245 
60 
■245 
230 
75 
•326 
220 
70 
■318 
220 
85 
■386 
220 
75 
■341 
200 
55 
•275 
195 
60 
■308 
215 
70 
•326 
210 
80 
■381 
225 
65 
•289 
225 
65 
■289 
265 
70 
•264 
250 
65 
■260 
210 
65 
•310 
195 
75 
■385 
245 
70 
•286 
240 
75 
■313 
255 
75 
•294 
245 
80 
■327 
175 
50 
•286 
170 
55 
■324 
230 
70 
■304 
230 
65 
■283 
250 
80 
•320 
245 
80 
■327 
240 
70 
•292 
235 
80 
■340 
230 
70 
■304 
220 
65 
■295 
240 
65 
•271 
230 
60 
■261 
210 
55 
•262 
200 
55 
■275 
235 
65 
■277 
225 
65 
■289 
220 
70 
•318 
220 
65 
•295 
240 
70 
•292 
230 
85 
■370 
240 
55 
■229 
225 
55 
■244 
225 
60 
•267 
220 
65 
■295 
245 
70 
•286 
235 
65 
■277 
245 
65 
■265 
245 
60 
■245 
220 
55 
•250 
210 
60 
■286 
235 
75 
•319 
225 
70 
■311 
230 
70 
■304 
220 
60 
■273 
250 
75 
•300 
245 
80 
•327 
220 
75 
•341 
215 
70 
■326 
225 
60 
■267 
220 
55 
■250 
255 
70 
•275 
250 
70 
•280 
240 
65 
•271 
235 
75 
■319 
230 
60 
■261 
225 
60 
■267 
260 
90 
•346 
255 
85 
•333 
280 
80 
•286 
270 
65 
•241 
220 
60 
■273 
215 
65 
■302 
230 
55 
•239 
215 
60 
•279 
250 
70 
■280 
245 
75 
•306 
235 
70 
■298 
220 
70 
■318 
220 
60 
•273 
205 
65 
■317 
210 
70 
•333 
205 
70 
■341 
215 
70 
■326 
215 
70 
■326 
240 
65 
•271 
225 
65 
■289 
185 
65 
■351 
185 
60 
■324 
250 
75 
■300 
245 
75 
■306 
220 
55 
•250 
205 
55 
■268 
225 
80 
■356 
225 
75 
■333 
240 
65 
■271 
235 
70 
•298 
235 
55 
•234 
235 
50 
■213 
190 
55 
■289 
175 
65 
■371 
255 
80 
■314 
245 
70 
■286 
275 
85 
•309 
275 
75 
■273 
250 
65 
■260 
240 
70 
■292 
275 
80 
■291 
275 
75 
•273 
205 
65 
•317 
200 
60 
■300 
240 
75 
■313 
230 
80 
•348 
265 
75 
■283 
250 
70 
•280 
215 
55 
•256 
205 
60 
•293 
200 
60 
■300 
190 
60 
■316 
230 
55 
■239 
205 
60 
•293 
250 
75 
■300 
235 
70 
•298 
170 
60 
■353 
165 
55 
■333 
300 
95 
■317 
300 
95 
•317 
235 
70 
•298 
220 
75 
•341 
200 
55 
•275 
190 
55 
•289 
235 
85 
■362 
225 
75 
•333 
210 
60 
•286 
210 
55 
•262 
220 
75 
•341 
200 
75 
•375 
250 
65 
■260 
245 
60 
•245 
250 
75 
•300 
250 
75 
■300 
230 
60 
•261 
220 
65 
•295 
190 
60 
■316 
185 
55 
•297 
250 
80 
•320 
245 
65 
•265 
220 
65 
•295 
210 
60 
•286 
235 
60 
■255 
225 
60 
•267 
255 
70 
•275 
245 
80 
■327 
235 
60 
•255 
220 
60 
•273 
230 
60 
■261 
225 
70 
•311 
225 
240 
65 
70 
•289 
•292 
205 
230 
70 
70 
■341 
■304 
indeed would appear to be the case for a short interval. Accordingly one should 
perhaps wait till the daughters are full-grown : on the other hand it may then 
be objected that the differences that are noticeable may be due to feeding or 
some modification of the environment. On the whole probably the fairest time 
at which to make the comparison is just shortly after division. I have attempted 
comparison at both stages. The measurements are taken at intervals of from one 
to thirty-two hours after division. A few further observations and statistics show 
a continued tendency to vary in the second generation. 
