Monthly Microscopical! 
Journal, June 1, 1869. J 
Boyal Mieroseopical Society. 
341 
minute waved line represented in some portions of Plate XIV. and 
Plate XVI., Fig. 4 ; tlie appearance is one that I cannot interpret 
with any certainty. 
The pseudo-tracheae of the central portion of the lips which 
open between the teeth appear shortly after their commencement 
(Plate XVI., Fig. 4) to curve beneath a fibrous band surroundins: 
the mouth, rising again to the surface just beyond, and continuing 
their course towards the margin of the disc. The chitinous semi- 
hoops at the oral end of the pseudo-tracheae have not the alternate 
forked and pointed arrangement, but are simple, and alternately 
long and short, like those main channels (Plate XVI., Fig. 2) ; the 
pseudo-tracheae which open into these channels have also the same 
simple arrangement of their skeleton where they join the larger 
channels. 
The two lobes of the lips when in a state of rest are folded 
upon each other, when in use they may be in any condition between 
this and ftdl extension ; or even with the margins turned back and 
the teeth prominent, the whole organ is so flexible and continually 
in motion that it is almost impossible to make even a rough sketch 
during the life of the insect. The difiiculty of observations upon 
the disc of the living fly is increased by the copious flow of saliva 
which, when the insect is under the influence of cliloroform, flows 
over the surface of the lips, and speedily prevents any details from 
being seen. 
With regard to the source of this flow of saliva, I quote at full 
length a communication received, with specimens, from Mr. J. G. 
Tatem, of Eeading, remarking that about the same time the dis- 
covery of the function of the salivary duct, before considered by 
him as a tracheal tube, was made by Mr. Lowne. 
" The salivary glands of the Blow-fly are long, much- con- 
torted tubes, of nearly equal diameter throughout; unravelled, 
they would probably exceed by one -half the entire length of the 
insect. Attached to either side of the oesophagus within the thorax 
they are closely bound to it by tracheal ramifications in two little 
bundles. The tubes become membranous, though more condensed 
and transparent as they pass through the cephalo-thoracic constric- 
tion into the head, where they send forward their ducts, which at 
the base of the proboscis unite to form a common duct extending 
to the chitinous tubular root of the so-called " lancet," or, as I am 
disposed to consider it, tongue. The ducts are, as usual, held open by 
a spiral filament of greater tenuity than that of the tracheae. Two 
flattened, ribbon-like nerves given off by the sub-oesophagal gan- 
glion accompany the ducts throughout their entire course, and 
terminate at the tubular base of the tongue ; probably ramifica- 
tions too minute for my detection spread to the lips and adjacent 
parts." 
