some Crustacea
(Apus, Palaemon) may prove them to be diplostichous in origin.

3. _The so-called_ "_Coxal Glands_."--In 1882 (_Proc. Roy. Soc_. No.
221) Lankester described under the name "coxal glands" a pair of
brilliantly white oviform bodies lying in the Scorpion's prosoma
immediately above the coxae of the fifth and sixth pairs of legs (fig.
27). These bodies had been erroneously supposed by Newport (12) and
other observers to be glandular outgrowths of the alimentary canal.
They are really excretory glands, and communicate with the exterior by
a very minute aperture on the posterior face of the coxa of the fifth
limb on each side. When examined with the microscope, by means of the
usual section method, they are seen to consist of a labyrinthine tube
lined with peculiar cells, each cell having a deep vertically striated
border on the surface farthest from the lumen, as is seen in the cells
of some renal organs. The coils and branches of the tube are packed by
connective tissue and blood spaces. A similar pair of coxal glands,
lobate instead of ovoid in shape, was described by Lankester in
Mygale, and it was also shown by him that the structures in Limulus
called "brick-red glands" by Packard have the same structure and
position as the coxal glands of Scorpio and Mygale. In Limulus these
organs consist each of four horizontal lobes lying on the coxal margin
of the second, third, fourth, and fifth prosomatic limbs, the four
lobes being connected to one another by a transverse piece or stem
(fig. 28). Microscopically their structure is the same in essentials
as that of the coxal glands of Scorpio (13). Coxal glands have since
been recognized and described in other Arachnida. In 1900 it was shown
that the coxal gland of Limulus is provided with a very delicate
thin-walled coiled duct which opens, even in the adult condition, by a
minute pore on the coxa of the fifth leg (Patten and Hazen, 13A).
Previously to this, Lankester's pupil Gulland had shown (1885) that in
the embryo the coxal gland is a comparatively simple tube, which opens
to the exterior in this position and by its other extremity into a
coelomic space. Similar observations were made by Laurie (17) in
Lankester's laboratory (1890) with regard to the early condition of
the coxal gland of Scorpio, and by Bertkau (41) as to that of the
spider Atypus. H.M. Bernard (13B) showed that the openin