70 SUMMARY OF CURRENT RESEARCHES RELATING TO 



large conical hollow processes protruding one on each side of the 

 anterior portion of the dorsal surface — perched right on the 

 prominent dorsal lobe. 



Dr. Hudson will figure and describe this new rotifer in the April 

 number of this Journal, together with another new species, also dis- 

 covered by Mr. Hood, F. longicaudata ; the latter has its footstalk 

 ending in a very long non-retractile pedicle, and forms also a 

 peculiar tube. 



Echinodermata. 



'Challenger' Holothuroidea.*— The first part of H. Theel's 

 Report on the ' Challenger ' Holothuroidea is devoted to the new 

 order Elasipoda, which name has with advantage been sub- 

 stituted for that of Elasmopoda, used in the Preliminary Report.f 

 Seven years have scarcely elapsed since the discovery in the Kara 

 Sea of the form for which this family was established, and now 

 over fifty species are known. These species of Elasipods are true 

 deep-water forms, and they may with all the more reason be said to 

 characterize the abyssal fauna, as no single representative, as far as 

 is at present known, has been found to exist at a depth less than 58 

 fathoms. Only one form, Elpidia glacialis, has been dredged at such an 

 inconsiderable depth, and even this was dredged in the Arctic Ocean, 

 where true abyssal forms are to be met with at comparatively shallow 

 depths. This species, too, can exist at immense depths, one from 

 Station 160 having been dredged at a depth of 2600 fathoms ; the 

 greatest depth at which any Holothuroid has hitherto been dredged 

 being 2900 fathoms. 



Among the more remarkable and distinguishing characteristics of 

 this order, Herr Theel mentions the agreement in several important 

 details — both in their internal anatomy and outer form — of the adult 

 and larval states ; an agreement more close than occurs in any pre- 

 viously known Holothuroid. He does not agree with Danielssen and 

 Koren in placing the Elasipods low in the series of the Holothuroids ; 

 nay, in some respects he regards them as having attained to a higher 

 development than all the other Echinoderms, because, among other 

 facts, their bodies are distinctly bi-laterally symmetrical, with the 

 dorsal and ventral surfaces distinct, and often with a cephalic region 

 well marked. Only the ventral ambulacra are subservient to loco- 

 motion ; these latter show a tendency to appear definite both as to 

 place and number. The dorsal appendages are so modified as to 

 perform functions different from the ventral ones. The report gives 

 full details of all the new species. 



Coelenterata. 



Nematophores of the Hydroida-J — C. de Mereschkowsky has 

 investigated the structure of the nematophores with regard to the 



* Reports on the Scientific Results of the Voyage of H.M.S. 'Challenger' 

 during the years 1873-6, vol. iv. (1882) 176 pp. and 46 pis. Cf. Nature, xxvii. 

 (1882) pp. 74-5. 



t See this Journal, iii. (1880) p. 268. 



X Bull. See. Zool. France, vii. (1882) pp. 280-1. 



