VOYAGE OF H.M.S. CHALLENGER.
REPOKT on the Pycnogonida, dredged by H.M.S. Challenger during the
years 1873-76. By Dr P. P. C. Hoek, Assistant at the Zootomical
Laboratory of Leiden University.
The beautiful and rich collection of Pycnogonida formed during the expedition of
the Challenger has been placed in my hands by Professor Sir W5rv^ille Thomson, F.R.S.,
for description in the official report of the voyage.*
Our knowledge with regard to the Pycnogonids in general, their systematic arrange-
ment, their geographical distribution, &c., is still very insufficient ; and with respect to
those of the greater depths of the ocean hardly anything is known.
The first attempt towards a monograph of the Pycnogonida is that of George
Johnston.^ His paper was published in 1837, and treats of the British species known up
to that time. Though no special paper on Pycnogonids seems to have been published
previous to Johnston's, yet there are several works of an older date, in which descrip-
tions of species and genera belonging to this group occur, as well as discussions as to
their place in the Zoological System. But as the descriptions are for the greater
part very incomplete and the species thei'efore not to be recognised, these works are
interesting only in so far as they show how much uncertainty has always been felt as to
the place of the Pycnogonids among the Arthropoda.
Linnseus (1767) ^ brings the forms known to him under the genus Phalangimn,
in which also numerous land-spiders are placed, and which he ranges between
Hydrachna and Aranea under his Insecta aptera.
'-I wish to tender my sincere thanks to Professor Sir WyviUe Thomson, F.E.S., &c., who liberally trusted to me —
though a stranger — the drawing np of this report ; at the same time to Mr John Murray who has kindly given me
much valuable assistance.
-George Johnston. — An Attempt to ascertain the British Pycnogonidoe, in The Magazine of Zoology and Botany,
conducted by W. Jardine, P. J. Selby, and G. Johnston, vol. i., 1837.
^ Carolus Linnjeus, Systema Naturie, editio xii. rev., 176&.
(ZOOL. CHALL. EXP. — PAET X. 1881.) â€¢ K 1