28 
PROCEEDINGS OF THE PERTHSHIRE SOCIETY OF NATURAE SCIENCE. 
or in what locality it begins. When we have ascertained 
this for a number of species,—and this we can only do by 
forming ample collections,—we will doubtless be able to 
obtain a glimpse of the causes which effect the variation. 
Having now endeavoured to show why it is desirable to 
form extensive collections of the Perthshire plants and 
animals, and to point out that the object of our Museum 
should be not only to afford an instrument of education to 
all who desire to learn, but if possible to be a means of 
adding something to human knowledge, let me offer a few 
suggestions as to how the collections are to be gathered to¬ 
gether. 
If we had plenty of money, it would be an easy matter, 
but, as it is, we must depend upon the exertions of individual 
members ; and though our progress may be slower, the 
work, I have no doubt, will be more thoroughly accom¬ 
plished, as it will be a labour of love. To demonstrate 
most effectively the distribution of species in Perthshire, it 
is necessary to divide the county into certain districts. In 
one of the early works published by the Society, a certain 
division into districts was adopted, and, with slight modi¬ 
fications, these divisions have been retained in a large map 
of Perthshire which has been prepared for the Museum. 
In the first place, the county is very naturally divided into 
two great districts—one lowland the other highland—by 
the line which separates the Devonian from the Silurian 
geological formation. This line passes through the county 
from south-west to north-east, and runs along the foot of 
the Grampian hills. If we stand on Kinnoull Hill, or any 
other of the Sidlaw or Ochil ranges, we can see at a glance 
the line of demarcation between these two great districts 
—the Devonian or lowland, and the Silurian or highland. 
These constitute by far the most important divisions, and 
their subdivisions are more for the sake of convenience 
than of indicating any striking differences in the distribu¬ 
tion. To this, however, there are exceptions. For ex¬ 
ample, the district which we call “ Gowrie,” and which 
includes all parts which drain into the tidal portion of the 
Rivers Tay and Earn, is in many respects peculiar. Again 
the districts situated in the basin of the Forth have several 
points of difference from those in the basin of the Tay. 
Moreover, the districts situated to the east of the Tay, 
Tummel, and Garry differ in some respects from those to 
the west of these rivers. The districts, then, into which 
we divide Perthshire are as follows :— 
1. Devonian Forth, and 2. Silurian Forth, including re¬ 
spectively the lowland and the highland districts of the 
Forth basin ; 3. Devonian Earn, and 4. Silurian Earn, 
separated as Forth is; 5. Gowrie, as defined above. 
Then, on the east of the Tay and Tummel, 6. Devonian 
Isla, and 7. Silurian Isla, being the lowland and highland 
division of the country lying between the watershed of the 
Sidlaws and the watershed (south) of the Tilt; 8. Athole, 
which includes the basin of the Tilt and most of the basin 
of the Garry; 9. Rannoch, including the greater part of 
the basin of the Tummel and Lochs Rannoch and Ericht; 
10. Breadalbane, which contains the basin of the Tay from 
Logierait upwards, including the River Lyon and Loch 
Tay and its tributaries; 11. Devonian Perth, and 12. 
Silurian Perth, embracing respectively the lowland and 
highland divisions of the district lying west of the Tay and 
between Breadalbane and the two Earn districts ; and 
finally 13, Lomond, the small part of the county which 
drains into Loch Lomond. As will be seen, the divisions be¬ 
tween these districts are well marked in most cases, and 
can easily be kept in mind in working at the fauna and 
flora. These districts, moreover, are well calculated to 
illustrate in a full degree many of the peculiarities of dis¬ 
tribution. In forming our collections, therefore, the first 
thing to be aimed at is to obtain a series of specimens 
illustrative of each of these districts. I say a series of 
specimens, for, except perhaps in the case of birds, which 
can move rapidly from one district to another, it is not de¬ 
sirable in most instances to base comparisons upon single 
individuals, and it is as easy to obtain and preserve several 
specimens of (say) a plant, an insect, or a mollusc, as one 
only. But in addition to illustrating the district in gene¬ 
ral, it will be well to keep in view the importance of ob¬ 
taining specimens from various parts of a district. In 
Gowrie, for example, specimens ought to be obtained from 
four or five localities, say, from the banks of the river at 
Invergowrie and at Perth; from places more inland; and 
from the summits of the Sidlaws. By this means the 
variation, if any exists, within a district can be ascertained. 
This, of course, applies only to species which are to be 
found in all the localities cited. As a matter of fact, it is 
only a comparatively small number that can perhaps be 
obtained in all the localities. 
It is unnecessary, I think, to dwell further on this sub¬ 
ject, as it must commend itself to everyone. We must 
now consider how the specimens are to be obtained. This, 
as already said, must depend on the assistance given by 
the members. I am glad to be able to report that assist¬ 
ance has already been promised and given by several 
members in different parts of the county; but if we are to 
carry out the scheme I have sketched of a full representa¬ 
tion of all the districts, we will require all the assistance 
we can get. We cannot expect, I need hardly say, to form 
our collections in their complete state all at once. That, 
indeed, will require ample time, but by working steadily 
