Rymer Jones, on Corethra plumicornis. 
L03 
fold themselves into an elaborate tracheal system ; and a pair 
of ear-shaped tubes, of which not the slightest trace could 
hitherto be discerned, make their appearance upon the dorsal 
aspect of the thorax ; two long tracheae seem to be thus simul- 
taneously produced, occupying the two sides of the body and 
constituting the main trunks, from which large branches are 
given off, to supply in front the head, the eyes, and the 
nascent limbs ; while posteriorly they spread in rich profusion 
over the now conspicuous ovaries, and terminate by ramifying 
largely through the thin lamellae that constitute the caudal 
appendages. The very act of this strange metamorphosis I 
have not been able to witness under the microscope, owing 
to the impossibility of predicating the exact period of its 
occurrence — but there is reason to believe that it takes place 
suddenly, and occupies but a short time in its completion. 
In individuals subjected to microscopic examination within a 
very brief period after their assumption of the pupa state, the 
places originally filled by the air-sacs of the larva are found 
to be occupied by the tattered remnants of their external 
coats, clearly indicated by ragged membranes, covered with 
patches of black pigment, in the immediate vicinity of which 
I have invariably met with numerous air-bubbles, extrava- 
sated as it were into the cellular tissue, as though forced out 
by some leakage during the violent disruption of the air-sac. 
I hope on a future occasion to lay before the Society a 
series of drawings, illustrative of the minuter details con- 
nected with this interesting process ; and, in case any of our 
members should be induced to devote a portion of their time 
to an investigation fraught with many difficulties, will at 
present merely say a few words which may probably serve to 
facilitate their operations, and save them much probation in 
the expensive school of experience. In their fresh condition 
these larvae are, from their very transparency, almost invi- 
sible ; and such is the translucency of their tissues, that these 
latter are with great difficulty distinguishable. To remedy 
this inconvenience, I have tried the effect of dyeing them 
with carmine and magenta, and of preserving them in a 
variety of solutions, but with no satisfactory result. So im- 
patient are they of endosmotic action, that they will not bear 
the slightest increase or diminution in the density of the 
surrounding fluid — at the touch of glycerine or syrup (how- 
ever much diluted) they shrink up into a shapeless heap, and 
by the weakest spirit are converted into masses of distortion. 
At last, driven almost to despair by their perversity under 
every mode of treatment, I was tempted to enclose them, 
while still alive, in cells filled with their native element — 
VOL. XV. i 
