NATURE 



165 



THURSDAY, DECEMBER 25, i< 



THE "CHALLENGER" REPORTS 

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

 "Challenger" during the Years 1S73-76 under the 

 Command of Cap/. George S. Nares, R.N., F.R.S., and 

 Capt. F. T. Thomson, R.N. Zoology— Vol. X. (Pub- 

 lished by Order of Her Majesty's Government, 1SS4.) 

 "\ 70LUME X. of the " Challenger Reports" consists of 

 » over 630 pages of text, and is illustrated by 80 

 plates ; it contains Parts xxvi. to xxx. of the Zoological 

 Reports, all of which have been brought out under the 

 able management of Mr. John Murray. It speaks a great 

 deal for the energy and speed with which the publication 

 of these Reports is conducted, when one notes that the 

 whole of the manuscript of this large volume was 

 only handed in between July 1SS3 and July 1SS4, and 

 that a portion of Dr. R. Bergh's memoir had to be 

 translated. 



The Report on the Nudibranchs is by Dr. R. Bergh. 

 Judging from the number and variety of species of this 

 group already described from tropical seas, it is probable 

 that it is to the tropics we should look for the head- 

 quarters of the group, and no doubt many and interest- 

 ing species are yet to be discovered there. As few 

 shallow-water dredgings were made during the cruise 

 of the Challenger, it is not to be wondered at that 

 the number of Nudibranchs collected was but twenty- 

 five, including only one deep-sea form. The majority 

 of the forms belonging to the Phylliroidae and /Eoli- 

 diadae collected during the cruise are pelagic, and are 

 represented by the genera Phylliroe, Glaucus, Fiona, 

 &c. ; some are littoral, such as Janolus australis, a 

 single specimen of which was taken in the Arafura Sea, 

 and one like the last referred to a new genus and species, 

 Cuthonella abyssicola, was taken with the trawl in the 

 Faroe Channel from a depth of 60S fathoms. Several 

 new species belonging to the Tritoniadse are described. 

 Of the Dorididee, two new genera and several new species 

 are diagnosed. Of these the most interesting is Bathy- 

 doris abyssorum. This differs from all others of the 

 family in the semi-globular form of the body, which is 

 somewhat like that belonging to the genus Kalinga of 

 Alder and Hancock, and which it also resembles in the 

 characters of its branchia, these being composed of 

 several separate branchial tufts, also in the development 

 of soft conical papillae upon the back. It has no frontal 

 appendage, and the dorsal margin is very slightly pro- 

 nounced. This new genus would appear to form a 

 remarkable connecting link between the Tritoniadae and 

 the Dorididse. The only specimen found was taken from 

 a depth of 2425 fathoms, at Station 271, in the middle of 

 the Pacific. Mr. Murray tells us that the body of the 

 living animal was gelatinous and transparent, the foot 

 was of a dark purple colour, the tentacles brown, and the 

 gills and other external organs orange. 



In an appendix, Dr. Bergh describes the only Onchi- 

 dium in the Challenger collection as U. melanopneumon. 

 Only one specimen was taken in shallow water, at Kan- 

 dara, Fiji. Although some would regard the Onchidia as 

 allied to the Nudibranchs, Dr. Bergh considers this view 

 entirely erroneous. With regard to their phylogeny they 

 Vol. xxxi. — No. 791 



have really nothing to do with Nudibranchs, and in 

 a quite recent article in Gegenbaur's Morphologisches 

 Jahrbuch (Band x. Heft 1, p. 172), he refutes the recent 

 views of J. Brock. For comparison with the new species 

 details of the anatomy of O. tonganum and O. verrucu- 

 latum are given. This Report is illustrated by fourteen 

 plates, for the most part devoted to anatomical details. 



Dr. L. von Graff's Report on the Myzostomida col- 

 lected during the voyage may be regarded as in some 

 sense a continuation of his monograph on this interesting 

 and little-known group. Of the 6S species enumerated in 

 this Report, 52 appear as new. These Myzostomes are 

 small disk-shaped animals, living attached to Crinoids 

 about whose affinities there has been up to the present a 

 good deal of doubt, some placing them among the Worms 

 near Tomopteris, others, as Dr. von Graff, among the 

 Arachnids near the Tardigrades ; and the discovery of a 

 new form among the Challenger collection seems to 

 confirm the correctness of this latter view. The author's 

 class of Stelechopoda embraces the Tardigrades, Lin- 

 guatulids, and Myzostomes, thus constituting a group of 

 very lowly organised Arthropods. This Report showf 

 that the Myzostomida do not form so uniform a group, 

 either as to their habits or structure, as was formerly 

 thought. It is prefaced by a very neat though brief 

 account of the general structure of Myzostoma as far as 

 it is known, with a graphic coloured diagrammatic repre- 

 sentation and most minute details as to the general mor- 

 phology, from which we condense the following important 

 statements. While all the hitherto known forms were 

 characterised by the peculiar radial arrangement of the 

 organs of the body, several species are here described in 

 which this arrangement is entirely lost ; in some {M. 

 folium) the body is greatly lengthened and the parapodia 

 and suckers are found arranged in two parallel lines, 

 while in a new genus (Stelechopus) not only has the 

 external radial symmetry disappeared, but not even are 

 the muscular septa and parapodial muscles convergent ; 

 hence, if, as the author believed long ago, the radial 

 arrangement was an adaptation to the mechanism of 

 fixation, or of the peculiar type of fixation, the want of it 

 as in Stelechopus, which doubtless is a freely moving 

 form, must be regarded as the primitive arrangement, 

 and thus intensifies the affinity to the Tardigrades. It is 

 interesting to find several forms entirely unprovided with 

 suckers, though in some they may exist as mere rudi- 

 mentary bodies ; in one species (.17. calycotyle) the 

 suckers are stalked. The suggestion so aptly made b\ 

 von Willemoes-Suhm that some of the Myzostomida 

 were in all probability dioecious, has been amply verified 

 by Dr. von Graff's researches. The two sexes when in- 

 habiting the same cyst are at times unlike in appearance, 

 the female being usually fifty to a hundred times as large 

 as the male. The cyst-producing Myzostomes are of 

 importance alike to the zoologist and the palaeontologist, 

 for these cysts have been found on the stalks of fossil 

 Pentacrini, and as Dr. von Graff is continuing his inves- 

 tigations into the fossil form, he will be most grateful to 

 any palaeontologists who, having collections of fossil Cri- 

 noidea under their care, would examine the specimens 

 and if they should notice the appearance of little pustules 

 at the base of the pinnules, would communicate the facts 

 to him. Of the sixty-seven species of Myzostomes 



