254 THR ZOOLOGIST. 
somewhat sudden demise of Prof. Thomas Spencer Cobbold, a Fellow of 
long standing, and who had contributed many important papers to the 
Society's Journals and Transactions, his latest paper being now in press. 
Dr. Cobbold had bequeathed to the Society's library sixty handsomely 
bound volumes, chiefly rare and valuable monographs on his special subject 
of parasites. A special vote of thanks was unanimously accorded by the 
Fellows to Mrs. Cobbold and family for the donation in question. 
Mr. Daniel Morris exhibited a number of living beetles (Pyrophorus 
noctilucus) from the island of Dominica. ‘These had been fed on sugar-cane 
during the voyage to England. On the meeting-room being darkened the 
phosphorescent show of light emitted was very brilliant. 
Mr. George J. Romanes then read a communication on “ Physiological 
Selection ; an additional suggestion on the origin of species.” He stated 
that, considered as a theory of the origin of species, Natural Selection 
encounters three cardinal difficulties: Ist, it cannot explain sterility 
between species, or the primary specific distribution; 2nd, it cannot 
explain many among the secondary specific distinctions, or those trivial 
details of structure which, while serving to distinguish one species from 
another, present no meaning of a utilitarian kind; 3rd, Natural Selection 
must always be so heavily handicapped by the swamping effects of inter- 
crossing upon any new variation, that unless such intercrossing is in some 
_way prevented, we may reasonably doubt whether Natural Selection alone 
could change one species into another in more than a very small percentage 
of cases, although, when intercrossing is prevented by the bar of sterility 
between species, Natural Selection may afterwards produce genera, families, 
orders, and classes. In view of these considerations Mr. Romanes con- 
tended that the theory of Natural Selection has been misnamed a theory of 
the origin of species. It is, in truth, a theory 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 on 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 habitual stations, &c. But it may also be done -by 
what he would call Physiological Selection, or by virtue of a variation 
taking place in the reproductive system in the direction of sterility ° 
(whether absolute or partial) with the parent form, without impairment of 
fertility within the varietal form. For instance, the season of flowering or 
of pairing may be either advanced or retarded in a portion of a species 
when all the individuals in that portion (or uew variety) would be absolutely 
sterile towards the rest of the species, while completely fertile among 
