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VI. The Prothoracic Gland of Dicranura vinula, and 
other Notes. By Oswatp H. Larrsr, Assistant 
Master at Charterhouse, formerly Tutor of Keble 
College. 
[Read March 3rd, 1897.] 
Prats V. 
i. THE Funcrion, AND SrrucrurRe, AND HoMmoLocies ox 
Proryoracic GLANDS. 
THE present communicaticn is the outcome and con- 
tinuation of my previous investigations, of which accounts 
are to be found in Trans. Ent. Soc. Lond., 1892, pp. 
287-292, and 1895, pp. 399-412. Being desirous of 
tracing the source of the potassium hydroxide solution 
by the aid of which the imago softens the cocoon at the 
time of emergence, and having already shown that this 
solution is stored in a special dorsal diverticulum at the 
anterior extremity of the mid-gut of the pupa, I pro- 
ceeded in the summer of 1895 to inquire into the nature 
of the alkaline fluid which is abundantly present in the 
alimentary canal of the larva. ‘I'wenty larvee in their last 
stage were procured, their alimentary canals were dis- 
sected out, and thrown into deci-normal hydrochloric acid 
of known weight and there minced, while the remainder 
of their bodies was likewise placed in another vessel con- 
taining hydrochloric acid of similar strength. 
I will deal with these latter first, for they led me to 
more complete results. 
On the day following the dissections above men- 
tioned I was astonished to find at the bottom of the 
beaker containing the hydrochloric acid into which the 
bodies of the larvee had been thrown, a thick gelatinous 
deposit covering all the bottom to a depth of about 
¢ inch. This deposit was semi-opaque, pale yellow 
in colour and sufficiently firm to allow of its being 
removed en masse from the beaker and of being 
lifted by one side without breaking or indeed bending 
TRANS. ENT. SOC. LOND. 1897.—pant u. (suLy) 8 
