1886.) Zoölogy. 653 
ZOOLOGY. 
PHYSIOLOGICAL SELECTION:—At a recent meeting of the Lin- 
nean Society, Mr. G. J. Romanes read a paper “ On physiologica 
selection: an additional suggestion on the origin of species,” 
The author contended that the theory of natural selection has 
been misnamed a theory of the origin of species. It is, in truth, 
atheory of the origin of adaptive structures, and, if unassisted by 
any other principle, could not effect the evolution of species. The 
only other principle that could here assist natural selection would 
be one that might mitigate the swamping effects of intercrossing. 
This may be done by geographical barriers shutting off a portion 
of a species from the rest, and allowing that portion to develop 
an independent course of varietal history without intercrossing 
with the parent form. It may also be done by portions of species 
migrating, changing habital stations, &c. But it mgy also be 
done by what the author calls physiological selection, or in virtue 
of a variation taking place in the reproductive system in the di- 
rection of sterility (whether absolute or partial) with the parent 
orm, without impairment of fertility within the varietal form. 
For instance, the season of flowering or of pairing may be either 
vanced or retarded in a portion of a species, when all the indi- | 
viduals in that portion (or new variety) would be absolutely sterile’ 
towards the rest of the species, while completely fertile among 
themselves, They would thus start on an independent course of 
variated history —Enghsh Mechanic. 
Mecuanics or Soarinc.—Professor Hendricks in the NATURA- 
List for June, imports into the “ mechanics of soaring” a momen- 
tary force which I do not think improves it. There is no “ mo- 
mentary” force concerned with any part of the activity that I am 
aware of. The birds are in the air quite early in the morning, 
and continue there until nightfall, all the forces concerned in their 
movements being active every instant of the time. 
ne air pressures beneath the surface produced by the normal 
notion are constant, and the expansion of these pressures against - 
the rear curve is constant, and this expansion gives the lateral ese 
motion. They are both derived from the gravitating force of the ae 
mass of the bird. There is no other force operative upon the 
bird in the act of soaring. ioe 
f ne 
