NA TURE 



121 



THURSDAY, JUNE 9, 1887. 



THE ZOOLOGICAL RESULTS OF THE 

 ''CHALLENGER" EXPEDITION. 



Report on the Scientific Results of the Voyage of H.M.S. 

 " Challenger^'' during the Years 1873-76 under the Com- 

 mand of Capt. George S. Nares, R.N, F.R.S., and of 

 the late Capt. Frank Tourle Thomson, R.N Prepared 

 under the Superintendence of the late Sir C. Wyville 

 Thomson, Knt., F.R.S., &c., and now of John Murray, 

 one of the Naturalists of the Expedition. Zoology — 

 Vol. XVIII. Parts i and 2, with a Volume of Plates. 

 (Published by Order of Her Majesty's Government, 

 1887.) 



VOLUME XVIII. of the Zoological Reports of the 

 Challenger Voyage well merits to be called enor- 

 mous, as it contains no less than 1800 pages. It contains 

 but a single memoir, " On the Radiolaria," by Prof. Ernst 

 Haeckel, of Jena, and is accompanied with a volume of 

 140 plates. 



A great work like this demands more than a passing 

 notice, for even in this age of scientific labour one stands 

 amazed at the physical energy, not to refer to the scien- 

 tific knowledge, that could have accomplished such a 

 result. Ten whole years of the author's life were devoted 

 to this monograph, which will ever be a worthy monument 

 of a most enduring kind. 



Some fifty years ago Meyen, and shortly after Ehren- 

 berg, first described some forms of Radiolaria. Meyen 

 has the merit of having observed and noted the first of 

 these curious forms in a living state, but to Prof. Huxley 

 we are indebted for the first accurate observations on 

 I some kindred forms met with by him during the voyage 

 ' of the Rattlesnake in the tropical seas. Ehrenberg no 

 doubt was the first to call attention to the exceedingly 

 great numbers of forms that were to be found in the 

 group, but although he was not ignorant of the researches 

 of his colleague, Johannes Miiller, whose memoirs were 

 published in the same Academy's Transactions as his 

 own, he never seems to have paid the slightest attention 

 to them, nor does he even allude to the name given to 

 the group by Miiller, that of Radiolaria, by which they 

 \ are now known. 



Just twenty-five years ago Haeckel published his well- 

 known " Monograph of the Radiolaria," which with its 

 splendid atlas of plates, was, and is still, an indispensable 

 work for the student. In this all the species known either 

 by figures or descriptions were reviewed, and arranged in 

 15 families and 113 genera, of which latter 46 were 

 new ; the number of forms observed alive amounted to 

 144, most of which are figured, in a manner that has not, 

 we think, been equalled, certainly not surpassed. 



In 1862, 7ittel described the first fossil Radiolaria from 

 the chalk; in 1876, John Murray established the family 

 Challengerida ; and above all, in 1879, Richard Hertwig 

 showed the essential differences in the formation called 

 the " central capsule," and in accordance therewith divided 

 the Radiolaria into six orders. From this on, with the 

 exception of the various important works on the fossil 

 forms by Emil Stohr, Dante Pantanelli, Butschli, Duni- 

 VoL. XXXVI. — N^. 919. 



kowski, and D. Rust, the whole record has been filled in 

 by Haeckel, and it has been almost exclusively based on 

 the collections of the Challenger. 



These Radiolaria, or Capsulate Rhizopoda, form a 

 peculiar class of the Rhizopoda — Haeckel's " Protista." 

 This class is exclusively marine, and, while possessing 

 many of the features of the Rhizopods, differs from them 

 in the possession of a peculiar " membrane" dividing the 

 cell-body into two distinct parts — the "central capsule" 

 or the internal part with the nucleus, and the external 

 part or " extra-capsulum " with the calymma ; the proto- 

 plasm of both parts communicates through fine pores, 

 which pierce the capsular membrane. The central cap- 

 sule is composed of three essential parts, viz. the central 

 nucleus, the intra-capsular sarcode, and the capsule 

 membrane. Besides these elements, the central capsule 

 contains very commonly an internal skeleton, fat and 

 pigment granules, crystals, and vacuoli. The outer part 

 of the Radiolarian body is also constantly composed of 

 the calymma, or a thick extra-capsular " jelly-veil." The 

 matrix or maternal tissue of the external protoplasm 

 and the pseudopodia again very commonly contains fat 

 and pigment granules, the skeleton and vacuoli, and, in 

 addition, " xanthellae " or " zooxanthellae," peculiar yellow 

 cells which contain starch, and are unicellular yellow 

 Alg£e living as " symbiontes " in true symbiosis with a 

 great number of Radiolaria. The skeleton may be either 

 siliceous or acanthinic, and is sometimes wanting. The 

 four sub-classes, as described in this Report, contain 20 

 orders ; and these, 85 families, which include 739 genera, 

 with 4318 species, of which latter 3508 are described as 

 new. 



Radiolaria occur in all the seas of the world, in all 

 climatic zones, and at all depths. Probably under normal 

 conditions they always float freely in the water, whether 

 their usual position be at the surface or at a certain depth 

 or near to the very bottom of the sea. Hitherto, no 

 observation has been recorded which justifies the assump- 

 tion that Radiolaria live anywhere upon the bottom of 

 the sea, either attached or creeping. However able they 

 may be to creep when they fall on a solid basis, they 

 seem normally always to float freely in the water, with 

 pseudopodia radiating in all directions. 



As regards their local distribution and its boundaries, 

 the Radiolaria show in general the same relations as 

 other pelagic animals. Since they are only to a very 

 slight extent, if at all, capable of active horizontal loco- 

 motion, the dispersion of the different species from their 

 points of development is dependent upon oceanic currents, 

 the play of winds and waves, &c. These passive migra- 

 tions are here, however, as always, of the greatest signi- 

 ficance, and bring about the wide distribution of indi- 

 vidual species in a far higher degree than any active 

 wanderings could do. Anyone who has ever followed a 

 stream of pelagic animals for hours, and seen how millions 

 of creatures closely packed together are in a short time 

 carried along for miles by such a current, will be in no 

 danger of under-esjimating the enormous importance of 

 marine currents in the passive migration of a marine 

 fauna. The number of cosmopolitan species which live 

 in the Pacific, Atlantic, and Indian Oceans is relatively 

 large. In each of three great ocean basins, too, many 

 species show a wide distribution. On the other hand^ 



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