160 Proceedings of the Royal Physical Society. 
eastern species, may be shown in the dispersal of certain 
others—viz., a west to east dispersal, locally escalading our 
mountain chains by sheer force of accumulated numbers, 
after all easier outlets and “avenues of escape” have first 
been overcrowded by migration, and afterwards overcrowded 
by actual permanent occupancy. Facts long accumulated 
enable me to at least indicate this possibility in the case of 
two species—viz., the Goosander and Merganser—species of 
as eminently western or north-western origin and concentra- 
tion, as the Tufted Duck is of earlier eastern occupancy. We 
also have numbers of facts which go to prove (or suggest, let us 
prefer to say) the courses of dispersal of many woodland species 
of totally different habits and powers, the movements of which, 
however, be it said, are often more intricate to follow. 
Readers will find further remarks in the forthcoming volumes 
by Mr Buckley and myself on “ The Moray Basin,” which we 
trust may be found worthy of perusal under several species, 
especially under a woodland species—the Redstart. 
Mr Hancock’s records show it to have been a breeding 
species in Northumberland as early as 1859, and Professor 
Newton writes me of what he considers the earliest record 
in Britain, viz.,in Nottingham in 1851. I am not aware, 
however, of any nesting sites in Northumberland which are 
located within the watershed of Tweed. 
XI. Note on the Occurrence of the Larva of the Drone-Fly 
(Eristalis tenax, Linn.) as a temporary Endoparasite in 
Man. By J. Antaur Tuomsoy, M.A. 
(Read 18th December 1895.) 
It has seemed to me useful to place on record what 
I believe to be, to say the least, very rare—the occurrence 
of the larva of the Drone-Fly (Hristalis tenaz, Linn.) as 
a temporary parasite in man. I make this note from a 
zoological standpoint; the physician in charge of the case 
will take account of the medical aspects. 
1 Vide Birds of Northumberland and Durham, p. 155. 
