1895.] MYODES LEMMUS. 25 
7. Breeding Conditions in å Prolific Year. 
In the prolific (and migratory) year 1891, during å re- 
sidence in the mountain distriets of Gausdal (a little way be- 
yond Lillehammer), I had an opportunity of making a number 
of observations on their conditions of propagation in their true 
home”. 
On my arrival in the middle of August, towards the close 
of the summer, the bulk of individuals consisted of young of 
the year, fully grown or nearly so, whilst there were compara- 
tively few of the old ones (which had wintered) remaining. 
These mostly die off in the course of the summer, and the mas- 
ses which migrate consist, chiefly, of the young ones, but å few 
months old. | 
The parents (from the previous year) had successively borne 
3, or in some instances 4 litters in the course of the summer. 
The first litter was probably born shortly after the com- 
mencement of spring. In August the young of this set were 
about the size of the old ones, and most of the females of this 
litter that I examined, were at this time again pregnant, or had 
milk in their teats. 
The second litter of young were, in August, somewhat more 
than half grown, and these do not appear, as a rule, to breed 
the same summer. One solitary young pregnant female which I 
examined, belonged either to a late first, or possibly to å second 
litter of the year. It had but two fætuses in the uterus. 
During August, the young of the third litter were about the 
size of a pigeon's egg, and still lay either in the nest, or re- 
mained in its immediate neighbourhood. The parents which 
suckled these young were, as å rule, pregnant with the fourth set. 

1) By the aid of å dog I could daily collect, on each excursion, from 
50 to 100 specimens of all ages, from new born young in the nest, 
to old ones from the previous year. 
