ISLAND LIFE. 
[rART I. 
64 
of mammalia. It will be interesting therefore to examine the 
few cases on record, as we shall thereby obtain additional know- 
ledge of the steps and processes by which the distribution of 
varieties and species has been brought about. 
Discontinuity of the Area of Pams palustris. — Mr. Seebohm, 
who has travelled and collected in Europe, Siberia, and India, 
and possesses extensive and accurate knowledge of Palaearctic 
birds, has recently called attention to the varieties and sub- 
species of the marsh tit ( Pams palustris) , of which he has ex- 
amined numerous specimens ranging from England to Japan. 1 
The curious point is that those of Southern Europe and of 
China are exactly alike, while all over Siberia a very distinct 
form occurs, the sub-species P. borealis. In Japan and Kam- 
schatka other varieties are found, which have been named 
respectively P. japonicus and P. camschatkensis. Now it all 
depends upon these forms being classed as sub-species or as 
true species whether this is or is not a case of discontinuous 
specific distribution. If Pams borealis is a distinct species from 
Par us palustris, as it is reckoned in Gray’s Hand List of Birds, 
and also in Sharpe and Dresser’s Birds of Europe, then Pams 
palustris has a most remarkable discontinuous distribution, as 
shown in the accompanying map, one portion of its area com- 
prising Central and South Europe and Asia Minor, the other 
an undefined tract in Northern China, the two portions being 
thus situated in about the same latitude and having a very 
similar climate, but with a distance of about 4,000 miles be- 
tween them. If, however, these two forms are reckoned as 
sub-species only, then the area of the species becomes con- 
tinuous, while only one of its varieties or sub-species has a 
discontinuous area. It is a curious fact that P. palustris and 
P. borealis are found together in Southern Scandinavia and in 
some parts of Central Europe, and are said to differ somewhat 
in their note and their habits, as w T ell as in colouration. 
Discontinuity of Emberiza schceniclus . — The other case is that 
of our reed bunting (Emberiza schceniclus), which ranges over 
almost all Europe and Western Asia as far as the Yenesai valley 
and North-west India. It is then replaced by another smaller 
i See Ibis, 1879, p. 32. 
