452 MURIDA:—AGRESTIS 
of the allied 17. avvalzs produced five young in captivity at the 
age of eighty-eight days on 2nd March, five more on 6th July, 
and again five on 30th July. The latter opened their eyes 
when ten days old. On the rath day, though still very small, 
they began to leave their nest. On the 26th day they appeared 
to be nearly “grownup.” In other respects the breeding habits 
are not known to differ from those of other mice, it being uncer- ~ 
tain whether they are monogamous or not. Probably in this 
respect their customs are as loose as in other gregarious mammals. 
The voice, often used in moments of excitement or hunger, 
is half a grumble, half a squeak." They do not seem to chatter 
their teeth and stamp their feet as some exotic species do. 
In captivity these mice are far more amiable than Bank Mice. 
Perhaps owing to poor brain power, they become tame very 
soon after capture, and can with difficulty be teased into biting. 
The young have been reared by a Field Mouse under the care 
of Mr F. H. Parrott? and by a House Mouse.® 
They are good swimmers. Mr Rope* has disturbed one 
amongst seaweed cast up by the tide, when it made for the 
water and swam out boldly. Mr Bruce Campbell has 
observed’ some swimming for pleasure in the sea in the 
Firth of Forth, at Long Green Bay, Dalmeny. 
Charles Darwin comments upon the dependence upon each 
other of Dutch and red clovers, humble-bees, and “ field mice.” ® 
The clovers are fertilised by the bees, and the numbers of the 
latter in any district depend in a great measure on the number 
of ‘‘ field mice,” which destroy their combs and nests, according 
to Colonel Newman, to the extent of two-thirds all over England. 
Darwin believed, again, that the number of mice is regulated 
by the lumber of cats, but here the correlation is doubtful ; his 
remarks are often read as referring to Field Mice,’ but the facts 
are probably true of several species, and the Grass Mouse is 
the most common in situations where humble-bees nest. Grass 
Mice also destroy a destructive sawfly,* which damages larch.® 
1 W. Evans. 2 Cocks. ° Rope, Zoologist, 1883, 332. 
* Zoologist, 1890, 330. 5 Ann. Scott, Nat. Fist., 1901, 48. 
“ The Origin of Species, 6th ed., 37th thousand, 1883, 57. 
* Apodemus sylvaticus. 8 Nematus erichsonit of Hartig. 
9 An exhibit to illustrate this fact was shown at the Royal Society’s conversazione 
on 13th May 1908, by C. G. Hewitt. 
