1895.] MYODES LEMMUS. 29 
neighbourhood, therefore before the emigration commences. 
During their stay in the lowlands they but exceptionally bring 
forth young; but no direct observations of their breeding habits 
during their pilgrimages have, so far as is known, been as yet 
made public. 
Personally, I have only on a few occasions found small 
younglings in the lowlands at such a distance from the moun- 
tain heights that they undoubtedly had been born on the jour- 
ney. Until the young are more than half grown they, on the 
whole, move about but little. The bulk of the migratory indi- 
viduals are, as mentioned above, young animals of the year, and 
still barely capable of propagation, and only in those instances 
in which the stay in the lowlands continues for another summer, 
can å reproduction occur. It, however, appears as if, on the 
whole, this cireumstance occurs but seldom. The abnormal con- 
ditions in which the individuals live, damps the inclination of 
propagation. Å 
The imerease of numbers. That the numbers can increase 
fo such an inordinate extent in some super-prolific years, is thus 
easly explained. 
The litters produced during the course of the summer, follow 
so closely, one upon the other that the ome set is barely allowed 
time to leave the nest ere the next lot arriwes.  Furthermore, the lit- 
ters are unusually large, as they constanily contain up to 10 young- 
lings im each set (although possibly 6 or 7 on the whole is the rule); 
and all these young ones appear to be possessed of greater powers of 
attaining maturity tham those produced during å normal year. 
Dr. Pleske, in his work on the Mammals and Birds of the 
Kola Peninsula, previously referred to, attaches great weight to 
the last mentioned circumstance, regarding it as being the prin- 
eipal cause of the wholesale increasel. 
I His opinion is: Dass in den giinstigen Jahren die jungen Lemmin- 
gen viel leichter aufkommen und gedeihen; gehalt man dies in 
Auge, so erscheint es als sehr möglich, das die Fortpflanzung in den 
