OLFACTORY BULBS OF THE ALBINO RAT 225 
TABLE 16 
Activity record of rats in revolving cages. for one hundred and three days. Series E 
A Ces Lata ints sine canes 914.5 8.9 aI is. a ees os. 559.7 5.4 
Vise eee ee i ei GD Z3M... 476.3 4.6 
OLY et eres Oe ee es Pa" oS 0 XeM.. 470.8 4.6 
BY Gear care nats ofl ODES 6.8 XoF... 458.7 4.5 
A ana oe: 2 a ee 689.0 Gerd Lig Rab Need Oe 457.1 4.4 
1, | ROC, «SOS 577.8 5.6 Tighe. # Mic ede ke 446.6 4.3 
Average for males...| 614.7 5.96 
Average for females} 593.7 5.76 
for females, and if we go back still further we get a still higher 
average for the females and lower for the males. The males 
were slow to begin to run the cages. An extreme example, Y, 
of the present series, ran less than 2 miles during the first five 
weeks in the cage, but became extremely active during the last 
four or five weeks making a final average of 5.4 miles per day, 
a record almost equal to the average for the entire lot of males. 
The females soon learned to run the cages and became very 
active at an early age. During the last weeks of the experiment, 
the activity of practically every female in the series was on the 
decline. I think from a study of all the records it may be con- 
cluded that while, in the revolving-cages, the females reach the 
period of greatest activity earlier than do the males, yet in the 
long run, the records of a large number of males and females 
would average about the same. 
Possible effect on fertility. There is some indication that the 
fertility of the albino rat is increased by exercise. In the cases 
of the three pairs of exercised rats which were mated, the fol- 
lowing record of offspring was obtained, together with the record 
of one control pair. 
The average size of litter for normal stock albinos has been 
found to be between 6 and 7 individuals (Donaldson 715). This 
is about the average for the control pair, while the averages for 
the three test pairs is considerably higher—13, 10.5, and 9. 
