THE 



VOYAGE OF H.M.S. CHALLENGEE, 



ZOOLOGY. 



REPORT 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 exjiedition of 

 the Challenger has been placed in my hands by Professor Sir WyvUle 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 therefore 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 Phalangium, 

 in which also numerous land-spiders are placed, and which he ranges between 

 Hydrachna and Aranea under his Insecta aj^tera. 



' I wish to tender my sincere thanks to Professor Sir Wyville Thomson, F.R.S., &c., who liberally trusted to me — 

 though a stranger— the drawing up of this report ; at the same time to Mr Jolm Murray who has kindly given me 

 much valuable assistance. 



2 George Johnston.— An Attempt to ascertain the British Pycnogonida, in the Magazine of Zoology and Botany, 

 conducted by AV. Jardine, P. J. Selby, and G. Johnston, vol. i., 1837. 



' Carolus Linnseus, Systema Naturae, editio .xii. rev., 1766. 

 a r (ZOOL. CHALL. EXP. PART X. — 1881) K 1 



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