SECTIONAL TRANSACTIONS.—D. 395 
Dr. E. S. Russet, O.B.E.—The migration of fishes (11.5). 
Dr. C. B. Witt1ams.—The migration of insects (11.30). 
Mr. G. A. STEVEN.—The growth and migrations of the Thornback 
Ray (12.0). 
During recent years ray-marking experiments have been carried out in 
the English Channel—in the vicinity of Plymouth—particularly on the 
Thornback Ray (R. clavata). Returns of marked fish have shown that, 
during the whole period of growth, from hatching to adolescence, the 
Thornback Rays, in the area investigated, are entirely non-migratory. So 
remarkably sedentary are these fishes during their immature years that in 
numerous instances the same fish has been captured again and again on 
exactly the same spot of ground in the open sea after intervals varying from 
two weeks up to almost two years. One fish, for example, has been 
captured and recaptured in the same place no fewer than six times at varying 
intervals over a period of fifteen months. 
Such repeat captures of the same fish at intervals over an extended period 
are unique in the history of fish-marking experiments and afford a valuable 
check on growth-rate data obtained in the ordinary way from the larger 
number of fish which are marked, liberated, and recaptured once only. 
From the data so far obtained, growth in R. clavata appears to be relatively 
slow, averaging about 5 cm. per annum increase in width of disc during the 
period of immaturity. 
Miss L. E. CHEesMAN.—The zoo0-geographical evidence of the former 
extension of land masses in the Western Pacific (12.30). 
The Austro-Oriental sub-region can be separated zoo-geographically 
into two divisions : a northern containing the Celebes and adjacent islands, 
and a southern (herein called Papuasia) which consists of New Guinea, 
definite areas in North Queensland, Aru and Key Islands, and islands 
east of New Guinea, including the Solomons and part of the New Hebrides 
Archipelago. Geological evidence of the land movements. Evidence 
deduced from the insect fauna. Deductions based on the Hymenoptera 
Parasitica. Distribution of Aculeate Hymenoptera influenced by man’s 
activities. Genera and species confined to Papuasia compared with those 
belonging to the entire sub-region. 
AFTERNOON. 
Mr. F. S. J. Hottick.—The flight of insects (2.15). 
If a dipterous fly, such as Muscina stabulans Fallén, is suitably held 
stationary relative to the ground, it will perform regular wing movements, 
and it is considered that an investigation of what occurs is of value in 
elucidating the process of normal free flight. 
The wing of a fly is capable of a certain degree of bending, and this, 
combined with the nature of the articulation, results in its attitude changing 
during each complete beat. It is possible to reconstruct the successive 
attitudes that make up the complete beat by studying the paths traced out, 
while the wing is vibrating, by the beams of light reflected from small 
mirrors attached to different parts of the wing surface. 
The velocity and direction of flow of air produced may be analysed by 
recording photographically the paths travelled by small particles carried 
along in the air-flow. 
