396 SECTIONAL TRANSACTIONS.—D. 
A consideration of these data shows something of the manner in which 
the insect is maintained in the air and propelled forwards ; first, by virtue 
of the effect due to the independent action of each wing, and secondly, 
due to that produced by mutual action of the two wings while at the top of 
their beat. 
Mr. J. M. Reynotps.—The nature of aptery in the Apterygota (2.45). 
A discussion of the secondary or primary nature of wings in Insecta, 
beginning with a review of proposed solutions of the problem. 
Lankester’s comparison with the Ratites is a mere analogy. Silc’s 
theory, based on the thoracic flaps of Lepisma, is not sufficiently supported 
by evidence. The fossil ‘insects’ from the Rhynie Chert are probably 
true Collembola, but there is no evidence as to whether or not they possessed 
wings. 'Tothill’s idea of balancing primitive and specialised features found 
in the Apterygota is unsatisfactory, because it excludes the possibility that 
the nature of the aptery in all three orders may not be the same. 
A detailed review of the characters of Machilis (‘ typical ’ of Thysanura) 
leaves little doubt that they are more primitive than the Pterygota in 
all respects, presumably including their aptery. The same is probably 
true of the Protura, but not of the more specialised Collembola. ‘These, 
however, may ultimately be shown to be primitively apterous by the dis- 
covery of an intact thorax of Devonian forms. 
The conclusions reached are supported on general principles by the 
relatively late appearance of wings in Pterygote development, suggesting 
that their evolutionary acquisition is relatively recent. 
Mr. E. A. Parkin.—Recent work on the food relations of the Lyctus 
powder-post beetles (3.15). é 
Morphological and histological examination of larve shows that there 
are no accessory glands appended to the gut, and that micro-organisms, 
present in a pair of mycetomes in the body cavity, can play no direct réle in 
digestion. Chemical analysis of the food and frass, determination of the 
enzymes present in the larval gut, the effect upon larval development of 
extracting wood with various solvents, and the results of some preliminary 
experiments upon feeding larve on powdered substrates such as wood of 
various species and wood flour mixed with different carbohydrates, etc., all 
show that Lyctus larve feed upon the cell contents and not upon the cell wall 
constituents of wood. Starch and a water-soluble factor, probably sugars, 
have been shown to be necessary for normal larval growth. Ovipositing 
beetles are able to detect wood suitable for larval development by chemo- 
tacticmeans. Wood rendered free from starch and sugars would be immune 
to Lyctus damage, and several methods to achieve this are now being 
investigated. 
Demonstrations on view during the meeting :— 
A series of living budgerigars in illustration of Prof. F. A. E. Crew’s 
paper to the Section. 
A series of specimens and slides illustrating ‘The pattern of the 
medulla oblongata in the Teleostean Fishes,’ by Dr. H. Muir Evans. 
A collection of fresh-water Polyzoa by Mr. H. E. Hurre.. 
A collection of Mycetozoa by Mr. H. J. Howarp. 
