SECTIONAL TRANSACTIONS.—C, D. 315 
sands and gravels laid down during an episode of Glacial retreat, and it 
seems probable that the platform was formed during a later episode of that 
retreat. 
SECTION D.—ZOOLOGY. 
Thursday, September 6. 
PRESIDENTIAL Appress by Dr. E. S. Russett, O.B.E., on The study of 
behaviour (10.0). (See p. 83.) 
Dr. D. S. MacLacan.—Cycles in insect epidemics (11.0). 
Dr. A. E. Cameron.—The biology of the Scottish Tabanide (11.30). 
Three genera of Tabanide occur in Scotland—Tabanus, Hematopota 
and Chrysops. 'The little-known life histories of these flies have been in- 
vestigated on account of their economic importance and in the hope that 
light might be thrown on the taxonomy of the group. 
Hematopota pluvialis, the Cleg, is the most prevalent species. Its larva 
has been hatched and reared. The larva is carnivorous and cannibalistic. 
Experiments on the peculiar organ of Graber, which is present in the 
posterior part of the abdomen of the larva, indicate that its function is the 
perception of vibrations. Such a function must be of great use to the 
larva in its natural environment in the soil. 
Adults of this species were induced to pair and lay eggs in the laboratory. 
The eggs were laid in masses of about one hundred and fifty, on leaves of 
grass or on the sides of the glass jar in which the flies were living. Oviposition 
followed a blood meal at an interval of ten days. A second oviposition 
may follow a second blood meal, but the second egg-mass is usually smaller. 
The life histories of several other species have been investigated. Some 
of these species are pests in the straths and glens of the Highlands and 
along the shores of lochs. These species lay egg-masses, which vary in 
form with the species. The larve of most species will feed on meat, but 
that of Chrysops relicta refused this diet. In this species the life history 
may last two years. 
Dr. J. F. G. WHEELER.—Drift-bottle work round Bermuda and its connection 
with the flora and fauna of the surrounding waters (12.0). 
The Bermudas lie in lat. 32° 19’ N. and long. 64° 49’ W. within the 
western border of the Sargasso Sea. Interest in the tides and currents of 
the islands was stimulated by one of the Governors, and a paper was pub- 
lished in 1844 based upon the reports of pilots and sea captains, but the 
results are confused. 
It is known in Bermuda that the Sea Bottle (Halicystis) is washed up on 
the south shore beaches from May to July, and it has been found that in 
the winter the Sargasso weed fauna is much sparser than it is in summer, 
some species of fishes and flatworms being entirely absent. The direction 
of drift of thirty-seven bottles recovered out of 530 liberated during two 
years suggests that during the winter the surface drift is from the north, and 
during the summer from the south-west. Halicystis lives in the Sargasso 
weed and is brought in bythe summer drift, which also brings large numbers 
