NOTES AND MEMOKANDA. 
281 
coincide, every tenth division on the scale shall cover the 
stage micrometer according to the power used. 
The Nutrition of Bisects. — “ I undertook, in September 1877, a series 
of researches on the nutrition of invertebrate animals, especially 
insects. My studies bore on the gaseous exchanges with the atmo- 
sphere at difterent periods of metamorphosis. 
I shall only call the attention of the Academy at present to 
the variations in the weight of the animal, above all, in the 
nymph or chrysalis state, in which the excreta are almost entirely 
gaseous. 
If we trace a curve, taking for abscissfe the times, and for ordi- 
nates the weights, from the egg to the perfect state, we find : — 
1. In the larval state the ordinates grow rapidly, to a maximum 
which corresponds to the moment when the larva ceases to feed ; the 
curve has the form of a sinusoid, with a few irregularities at the times 
of casting the skin; beyord the maximum the ordinates decrease, 
forming a descending branch of another sinusoid. 
2. Ifiiis curve continues during the early times of the nymph ; 
but starting from the ‘ confirmed state ’ of M. Dufour, when, in the 
Lepidoptera and Diptera which I studied {Bomhyx mori, Musca 
vomitoria, &c.), the weight is i educed to half the value which it had 
attained in the larva, the variations become much smaller, the curve 
is changed into a straight line slightly inclined to the axis which re- 
presents the times ; the inclination always increases in the latter days 
of the nymph. 
3. At the moment of escape, there is an abrupt diminution of 
weight by the loss of the envelopes. During the short state of im- 
maturity there are rapid alternations of augmentation and diminution 
of weight. (Here follows a diagram of the curve.) 
4. In the perfect state and when the animal is taking food, there 
are successive augmentations of weight, which may reach and surpass 
the maximum weight of the larva, and become almost triple what it 
was at the time of escape ; there are, moreover, temporary variations 
of this weight, in different conditions of movement or repose, of light 
or darkness, &c. In the animal subjected to starvation from the time 
of escape, death supervenes after a loss of weight, which in different 
individuals belonging to the same species, is a sensibly constant frac- 
tion — among the Diptera about half the initial weight. 
The investigations above mentioned as to the gaseous exchanges, 
allow of the explanation of the greater number of these facts, which 
throw light on the physiology of invertebrate animals.”^ 
Parasites on a Diatom . — M. Guimard, a corresponding member of 
the Belgian Microscopical Society, communicated to the Society, at 
their July meeting, a circumstance that he observed in examining 
some diatoms, mostly consisting of Pimiularia, which he gathered at 
the seaside. He was astonished to see a great number of the diatoms 
covered by small bodies of a yellowish brown colour, and moving 
with great rapidity. With a No. 5 of Nachet they were seen to have 
* M. L. Joulin, in ‘Comptes Rendns,’ vol. Ixxxvii. p. 384. 
VOL. I. • X 
