COXJUGATIOX IN PARAMECIUM 
291 
of the hay to diffuse, so that the period of conjugation was not 
reached till February 25. 
At intervals samples of each of the sets were removed and meas- 
ured. As shown in my paper of 1909, abundant nutrition causes 
the animals to become much broader. At the same time, if rapid 
multiplication occurs, the animals ma}' become a little shorter; 
whether this happens depends upon the relation of multiplication 
to growth. The breadth is therefore the dimension to examine 
in judging as to the nutritive condition. The measurements 
show clearly the relation of the conjugation period to growth 
and to hunger. They are as follows : 
NO. 
MEASURED 
LENGTH I 
N MK RONS 
BREADTH IN ^. 
IICRONS 
Old culture; no fresh food 
53 
132.30 
± 1 
.59 
27.96 ^ 
.43 
Same, after twenty-four hours in 
fresh hav infusion 
41 
127.56 
=fc 1 
.19 
41,37 ^ 
.55 
Same, after three days in the new- 
infusion; conjugation beginning. 
69 
122.10 
± 1 
.16 
1 28.90 ± 
.26 
Thus, when the animals were placed in the fresh infusion, their 
breadth increased by 47.9 per cent in twenty-four hours. Later 
the breadth decreased again, and when it had, after three days, 
reached almost precisely the original breadth, conjugation began. 
Outlines of characteristic specimens at the three stages are shown 
in fig. 4. 
The same relations are brought out if one examines the Para- 
mecia of the large old culture, to which dry hay was added (d 
and e, above). Three days after the hay was added the animals 
were noticeably larger and thicker. Now a watch glass of the 
infusion, with many specimens, was removed to the moist cham- 
ber for twenty-four hours. At the end of that period the animals 
had decreased in size, and conjugation was beginning. The 
measurements are as follows: 
\ 
