1901) MICROSCOPICAL JOURNAL. 301 
pro- and meso-thorax. From the exterior free edge pro- 
ject hollow arborescent chitinous rods, which curveo ut- 
wards and interlock for about one-third of the length of 
the spiracle. These rods are hollow, even to the minu- 
test twigs, which have a free opening at their points. 
Close behind is a transparent membrane, the true valve. 
It is united to the wall of the large tracheal vesse] which 
extends across the thorax to the opposite spiracle. The 
free edge of the valve is closely set with a chitinous fringe. 
A special muscle arises from the integument at the lower 
end of the spiracle. By the contraction of this muscle 
the free edges of the valve would be caused to approach 
each other. From the integument another set of muscles 
arises, which are directed towards the valve, but whether 
they are connected with it I have not been able to deter- 
mine. Antagonistic muscles are a necessary consequence 
for working the valve. 
PRoOBoscis oF BUTTERFLY.—The tongue, or proboscis, is 
a cartilaginous substance, and owes its great flexibility 
to being formed in rings, which give it a finely-engraved 
appearance under the microscope. It is formed of two 
pieces that can be separated through its whole length, 
and each being grooved on the inner side they fit to- 
gether perfectly air-tight ; this is effected by an infinite 
number of fillets resembling the lamine of a feather which 
interlace and adhere to each other. Between this groove 
and the outer skin is a space occupied by trachew or 
the breathing tubes. The proboscis is always carried 
coiled, but can be uncoiled in a moment. It is perfectly 
suited to the work of penetrating to the honey of flowers. 
We know how butterflies close their wings as they alight 
or a flower, when the insect makes a powerful expiratory 
éifort by which the air is expelled from all trachex. At 
the moment of applying its proboscis to the food it makes 
an inspiratory effort by which the tube of the proboscis 
