Cheshire then settles the question which has been in dispute since the time of Swammerdam, whether the bee’s tongue is solid or tubular. He agrees with Wolff that the duct is a trough and not a tube, and proves it by a satisfactory experiment. He remarks:
FIG. 87.—Longitudinal section through the head of the honey bee, ♀, just outside of right antenna: _ant_, antenna with three muscles attached to _mes_, mesocephalic pillar; _cl_, clypeus; _lbr_, labrum; 1, chyle-gland (system no. 1, of Siebold); _o_, opening of the same; _oc_, ocellus; _br_, brain; _n_, neck; _th_, thorax; _oe_, œsophagus; _s.d_^2, _s.d_^3, common salivary ducts of systems 2 and 3; _v_, salivary valve; _c_, cardo; _ph_, pharynx; _mx′_, labium; _mx.′p_, labial palpi; _mt_, mentum; _mx_, maxilla; _hyp_, hypopharynx; _s_, bouton.—After Cheshire. ]
“Bees have the power, by driving blood into the tongue, of forcing the rod out from the sheath, and distending the wrinkled membrane so that in section it appears as at _H_, Fig. 86, the membrane assuming the form of a pouch, given in full length at _A_. It will be seen at once that this disposition of parts abolishes the side ducts, but brings the central duct to the external surface. The object of this curious capability on the part of the bee is, in my opinion, to permit of cleaning away any pollen grains, or other impediment that may collect in the side ducts. The membrane is greasy in nature, and substances or fluids can be removed from it as easily as water from polished metal. If, now, the sides of a needle, previously dipped into clove oil in which rosanilin (magenta) has been dissolved, so as to stain it strongly red, be touched on the centre of the rod, the oil immediately enters, and passes rapidly upwards and downwards, filling the trough.”
=Does the hypopharynx represent a distinct segment?=—The facts which suggest that the hypopharynx may possibly represent a highly modified pair of appendages, arising from a distinct intermaxillary segment, are these: Heymons plainly shows that, in the embryo of Lepisma, the hypopharynx originates as a transverse segment-like fold in front of the 2d maxillary segment, and larger than it, and though he does not mention it in his text, it appears like the rudiment of a distinct segment; the hypopharynx of Ephemeridæ; arises and remains separate in the nymph from the labium (see Heymons’ Fig. 29, and there are two lateral projections; see also Fig. 72, and Vayssiere’s view that it may represent a pair of appendages; Kolbe also regards it as representing a third pair of maxillæ, his endolabium, p. 213). Though what is called an unpaired organ, it is composed of, or supported by, two bilaterally symmetrical styles, both in Myriopods (Fig. 6, labiella, _stil_) and in insects (Fig. 77, etc.). On the other hand, in the embryo of pterygote insects, an intermaxillary segment has not been yet detected.