486 



NA TURE 



[Sept. 1 8, i! 



are described as new. The occurrence of two kinds of 

 polyps differing chiefly in size is noted in a new species 

 of Melitodes. The Sponge collection was large, com- 

 prising over 300 specimens, representing 1 10 species, be- 

 sides 7 distinct varieties, of which more than half were 

 well preserved in spirits ; a large proportion — 42— were 

 new. More than one-sixth belonged to the Ceratosa, <S6 

 to the Silicea, with no representatives of the sub-order 

 Hexactinellida, and there were but three species of 

 Calcarea. The author deserves great credit for the pains- 

 taking way in which he has described every form, so that 

 no doubt might remain as to its character ; and where 

 there was the slightest doubt of the form being a new 

 species he has refrained from possibly adding to an 

 already over-burdened synonymy. 



The description of the collections from the Western 

 Indian Ocean forms the second part of this volume, and 

 occupies about 150 pages. The reporters are the same as 

 in the previous part. Among the birds, Mr. Sharpe 

 describes a new Turtle Dove (Tint 11 r coppingert) from 

 Glorioso Islands. Mr. Edgar Smith's list of Mollusca 

 " may be regarded as an appendix to E. von Martens's 

 work on the 'Mollusca of the Mauritius and the Seychelles'; 

 of the 121 species noted, between 40 and 50 do not occur 

 in Mobius's work, and the majority of them, as might be 

 expected, are well-known forms." Thirteen new species 

 are described and figured. 



Forty-eight species of Echinoderms are tabulated by 

 Mr. F. Jeffrey Bell. The only object of special interest 

 is a remarkable new Ophiurid, for which a new genus, 

 Neoplax, has been established ; N. ophiodes was found at 

 Darros Island, Amirante Group. 



The collection of Crustacea, described by Mr. E. J. 

 Miers, though less numerous in species and less interesting 

 than those obtained on the Australian coasts, contains a 

 large number of rare and undescribed forms, partly owing 

 to the fact that the groups of islands known as the 

 Amirante, Providence, and Glorioso Groups have hitherto 

 been unknown to the carcinologist ; 104 species and 

 varieties are enumerated from the African sub-region, of 

 which 16 species are described as new. A useful table 

 showing the distribution of the species on the East Coast 

 of Africa and islands adjacent is appended to this 

 Report. 



Mr. C. O. Waterhouse describes a new beetle (Cratopi/s 

 adspersus) from Eagle Island (Amirante), and Mr. A. G. 

 Butler a new moth {Deiopeitt lacted) from Providence 

 Island (Mascarines). 



The series of Alcyonaria and Sponges, as before, are 

 described by Mr. Stuart O. Ridley. The collection of 

 Alcyonarians made was small, not, we should imagine, be- 

 cause the dredgings were limited to depths not exceeding 

 30 fathoms, but to the difficulties of collecting on and 

 under coral reefs. Probably the same difficulty was in 

 the way of a collection of Zoar.'J.aria being made, though 

 notably species abound all around these Western Indian 

 Ocean Islands. Of the S species of Alcyonaria, 2 are 

 noted as new. The collection of Sponges was mure 

 important, containing as it did 56 species, of which 21 

 are described as new. In a survey of the species (lie 

 author notes that, " notwithstanding the large proportion 

 of new specific forms, there is a comparative scarcity of 

 forms showing marked distinctive characters of generic 



importance which are not also to be found in the more 

 familiar Atlantic fauna." Indeed this western part of the 

 Indian Ocean may be considered, so far as the Sponge 

 fauna goes, as transitional between Australia, South-West 

 Africa, and the Mediterranean. 



LETTERS TO THE EDITOR 



[ The Editor does not hold himself responsible for opinions expressed 

 by his correspondents. Neither can he undertake to return^ 

 or to correspond with the writers of, rejected manuscripts. 

 No notice is taken of anonymous communications. 



[7 he Editor urgently requests correspondents to keep their letters 

 as short as possible. The pressure on his space is so great 

 that it is impossible otherwise to insur, the appearance even 

 of communications containing interesting and novel facts. ] 



The Flow of Streams 



The inclosed notes by my friend Mr. George Maw of Ben- 

 tlia.ll Hall will no doubt interest some of your readers. They 

 were communicated by me to Sir Wm. Thomson, who made 

 the following remarks upon them : — " Mr. Maw's notes are ex- 

 tremely interesting. I lately observed similar phenomena in the 

 streams flowing from the pools on the Burbo Bank near Liver- 

 pool. You ought to send them to Nature." 



Dear Mr. Smith, — As I know you have been making ob- 

 servations on river currents and the effect of friction on the 

 motion and passage of streams, I cannot resist sending you the 

 accompanying notes on a very curious case we met with near the 

 Lake of Thun. It is an extreme illustration of the action of 

 gravitation and friction working, as it were in opposition. I 

 have often observed something of the same kind before, but 

 never so well marked. Looking up the stream from the lake, 

 the effect was just like a long ladder of low waves approaching 

 you, each separately breaking over a low fall into the lake. 

 Believe me very truly yours, 



George Maw 



Hotel and Pension Ober, Interlaken, June 29 



Notes on a Pulsating or Intermittent Stream at Mertigen, on the 

 Lake of Thun 

 The intermittent flow of streams familiar to us, from the rapid 

 pulsation of the cataract to the slower rise and fall at regular in- 

 tervals of less precipi'ous streams, is strikingly illustrated in a 

 mountain stream flowing into the Lake of Thun, near Merligen. 

 The lower part of its course over a small talus or sloping delta 

 has been artificially banked up as a straight channel 15 feet 

 wide, evenly paved and walled with stone. The lower part has 

 an inclination of about one in twelve, and the upper part towards 

 the mountain gorge a slope of about one in nine. It flows directly 



into the lake, and, viewed from the lake, presents a remarkable 



appearance. 



The fall into the lake pulsates at intervals of 3J seconds by a 

 sudden increase of volume, and the stream above, flowing over 



