324 JOURNAL OF THE PLYMOUTH INSTITUTION. 
it jammed it between itself and a stump of dead ling sticking up 
outside, elevating its own body with its burden on top by driving 
the tips of its wings and its hooked tenacious claws into the fabric 
of the nest. It did not effect its purpose while I watched it, for 
perhaps over half an hour, on account of the bunches of ling and 
tufts of grass around those parts of the nest to which, unfor- 
tunately for itself, it happened to bring its burden. So much 
was the nest enclosed, that the only place where it was likely to 
have succeeded in throwing it out was at the spot where I found it 
at first. The instinct of the young cuckoo shown in ejecting the 
nestlings of the foster species is one so wonderful that Darwin has 
considered it a fit subject for special remarks when combating 
objections to his natural selection theory. The facts concerning 
the young cuckoo capitally illustrate the warfare and interdepen- 
dence of species at the same time, for, whilst warring against the 
foster species in the aggregate, it is yet dependent on individuals 
among them for its power to exist as a species. 
Our native quadrupeds are so few that a great number of cases 
illustrative either of species warfare or species interdependence 
could not be brought forward with reference to them. This class 
however furnishes us with one striking instance of the general 
diffusion and rapid increase of an introduced species causing a wide- 
spread and general decrease of a congenerous native one. I allude 
to the Norwegian, and now common, rat, versus the old English, and 
now extremely rare and local, black rat. I was greatly surprised 
to find, from a statement in an interesting article in the ‘“ Zoologist” 
for April last, contributed by one of our members, Mr. Francis H. 
Balkwill, that the black old English rat still exists about the 
Messrs. James’ Starch Manufactory at Sutton Road. It would be of 
great interest to find some reason for its long continuance in this spot. 
The introduction of so many foreign plants and shrubs into our 
gardens and pleasure-grounds has doubtless increased the numbers 
of certain insects, and probably birds also, as many of these aliens 
furnish food for both. Amongst insects the death’s-head hawk 
moth (Acherontia Atropos) has probably benefited as a species by 
the very general cultivation of the potato; for it is on this 
American plaut that the caterpillar most frequently feeds, though 
sometimes on Lycium barburum, a common shrub from N. Africa, 
or else on the jasmine from the East, and, what is remarkable, only 
comparatively rarely on any indigenous plant. 
