486 SECTIONAL TRANSACTIONS.—D. 
SECTION D.—ZOOLOGY. 
Thursday, September 7. 
PRESIDENTIAL AppreEss by Dr. J. Gray, F.R.S., on The mechanical view 
of life (10.0). (See p. 81.) 
Mr. E. Heron-ALten, F.R.S.—Diffusion and extension phenomena 
observed in the behaviour of living protoplasm (11.0). 
Dr. G. P. Bripper.—The energy of flagellate cells (11.30). 
My estimate of the work done per second per gramme weight of sponge 
flagellate cells (Brit. Ass, Report, Leeds, 1927, p. 73) was a modification of 
calculations explained to the Society of Experimental Biology in 1924, 
based (a) on velocities observed in isolated cells compared with rate of 
vibration of their flagella ; (b) on a priori calculations from size and rate of 
vibration of the flagella; (c) on the observations of velocity from the vent 
of Leuconia (= Leucandra) aspera, resistance in its channels, and the number 
of its collar cells, described to Section D at Hull (O.7.M.S., 1923, p. 293). 
Through Prof. Dohrn’s kindness, I made in 1932 new experiments at 
Naples on the current from the vent of L. aspera, afterwards weighing 
alive in sea-water the sponges used. The improved experiments have 
made it possible to calculate the oscular velocity from each observation of 
the further part of the jet ; they verify the theoretical conclusion (O.7.M.S., 
1923, Pp- 320) that the oscular velocity is characteristic of the species, and 
irrespective of size of individual. With this velocity the determination of 
the protoplasmic volume gives a solid datum for a more certain estimate of 
the useful work done per gramme of collar cells—necessarily very small 
compared with the efficiency of purely motor protoplasm. 
Dr. V. B. WiccLeswortH.—The réle of water in the physiology of 
excretion in insects (12.0). 
The elimination of waste products, particularly the elimination of nitrogen, 
with the least possible loss of water is one of the chief problems with which 
insects, in common with all terrestrial animals, are faced. Insects discard 
their nitrogen chiefly as uric acid, which can be readily precipitated and 
excreted in solid form. In the blood-sucking bug, Rhodnius prolixus, the 
precipitation of free uric acid is brought about by the secretion of urate in 
solution in the upper parts of the Malpighian tubes and the reabsorption 
of base and of water in the lower parts. In many insects a further mechanism 
for the recovery of water exists at the hind end of the gut, where the so-called 
rectal glands, or the general rectal epithelium, reabsorb water from the 
excrement before it is allowed to leave the body. In the aquatic larva of the 
mosquito, the so-called anal gills, which bear a superficial resemblance to 
prolapsed rectal glands, absorb water from the surrounding medium so 
that a constant supply is available for excretion, and only when this absorp- 
tion is prevented experimentally does solid uric acid appear in the excretory 
system. 
Dr. Georcr SALT.—Experiments on the behaviour of insect parasites (12.30). 
Most animals are capable of increasing their numbers very rapidly, -but 
are prevented from doing so, partly by carnivorous animals that prey upon — 
