1895. RESULTS OF ''CHALLENGER'' EXPEDITION. 59 



.^roup as equivalent to the Arachnida or Crvistacea, but perfectly 

 distinct from both. 



Unfortunately, no light was thrown upon the origin and affinities 

 •of the Pycnogonida by Dr. Hoek's researches in connection with the 

 species obtained by the " Challenger." But in other respects con- 

 siderable additions to our knowledge were made. Representatives of 

 thirty-six species, belonging to nine genera, were collected, and of 

 these thirty- three species and three genera had to be described as 

 new. Moreover, a striking fact connected with the bathymetrical 

 range of the genera was discovered, namely, that, with one exception, 

 the genera dredged in deep water were represented also by littoral 

 forms. In a few cases, indeed, specimens of the same species were 

 obtained at very varying depths. For instance, Nymphon gvossipes at 

 83 and 540 fathoms, Colossendeis leptovhynclms at 400 and 1,600 fathoms, 

 and Pcdlenopsis patagonica at 45 and 175 fathoms. The genus Oorhynchiis 

 <{P1. xiv., Fig. i) is the only one that has no representative in shallow 

 water. Lastly, it was observed that the conditions of life in the deep 

 sea have by no means had a dwarfing effect upon these animals. On 

 the contrary, many of the deep-water species attain a size which is 

 never equalled by those near the coast. The largest species procured 

 was Colossendeis gigas, a specimen of which spanned nearly 2 feet 

 from toe to toe. 



Tracheata and Malacopoda. — Since marine biological research 

 was the main object of the cruise of the " Challenger," and collecting 

 -excursions on land rarely possible for the naturalists on board, it is 

 •easy to understand why the scientific descriptions of the strictly 

 terrestrial forms of life find no place among the formidable array of 

 volumes in which the researches upon the pelagic species are so 

 elaborately set forth. Seeing, nevertheless, that many of the localities 

 visited are islands, isolated and out of the beat of the ordinary run of 

 "vessels, and for this reason rarely, if ever, explored by collectors, it is 

 not surprising that many of the species obtained proved to be of con- 

 siderable zoological importance. 



From a morphological point of view, there is no doubt that the 

 onost valuable of all the land Arthropods was the genus Peripatns, 

 •which Professor Moseley came across on the slopes of Table Moun- 

 tain. The existence of this curious animal, half annelid, half centi- 

 pede, had been known for many years ; but its true position in the 

 animal kingdom had remained up to that time an unsolved problem. 

 The dissection, however, of freshly-killed specimens of the Cape 

 species and a study of some of the stages of its development, enabled 

 this able zoologist to point out once and for all, by means of the dis- 

 •covery of the tracheal nature of its respiratory organs and the appen- 

 dicular character of its jaws, that it must take rank as the most 

 primitive of Tracheate Arthropoda. 



Very interesting, too, was the collection of Centipedes and 

 Millipedes, which, though small in numbers, was relatively rich in 



