MATERIAL AND METHODS 9 



Since the return of the ' Mabahiss ', our knowledge of the Indian Ocean siphonophore fauna has 

 been supplemented by a study of eight more collections. The first was a rich collection made by 

 R.R.S. 'Discovery II' which, in 1935, ran a line of stations up from Marion Island to the Gulf of Aden. 

 From the plankton taken at these 'Discovery' Stations I have picked out and identified about 14,000 

 specimens. They fall into some 170 categories which represent the parts of polygastric and eudoxid 

 colonies of seventy-six species. They were taken in forty-five tow-net hauls (Stations 1566-89), fished 

 at various depths between the surface and 1900 m., all being closing-net hauls. These 'Discovery' 

 Stations provide records of twenty-one known Siphonophores not previously recorded from the 

 Indian Ocean, and not taken by the 'Mabahiss'. In addition a number of new species were taken 

 at these ' Discovery ' Stations : three of these have been known to me for a long time, though descrip- 

 tions have not yet been published, and some others are new to me. There are a few other novelties 

 which will not be mentioned until more is known about them. 'Discovery's' N70V series of nets 

 in particular gave valuable results, and I have separated out no less than 11,000 Siphonophores, 

 including larvae, from these catches. 



The next collection was made in the Red Sea in 1935-6 by Cdr. J. H. Bowen, R.N., in H.M.S. 

 ' Weston '. 



Another line of stations across the Indian Ocean was made in 1936 by R.R.S. 'Discovery II' in 

 lat. 32 S., at which thirty-five species of Siphonophora were taken in twenty-nine closing-nets. 



A fourth collection was made between November 1948 and February 1949 in the Gulf of Aden by 

 Mr A. Fraser-Brunner, while investigating the fisheries of the Aden Protectorate. Off Aden he 

 fished a metre net both by day and night, by anchoring the boat and streaming the net out with the 

 tide, allowing it to fish for half an hour and hauling it. Off Bulhar, Mukalla and Alayu he also fished 

 the same net for half an hour just below the surface at a towing speed of about three knots (see Chart, 

 p. 10). 'Discovery II' made four stations, Nos. 2679-82, in the Gulf of Aden in 1950. I have 

 examined the oblique haul from 200 m. to the surface made at Station 2681. In 195 1 she made another 

 station there, No. 2900. 



A fifth collection of 925 specimens was made in the Gulf of Aqaba by the British Museum (Nat. 

 Hist.) Expedition in M.Y. 'Manihine'. Thirty-two stations were made between 31 December 1948 

 and 3 February 1949. Thirteen species of Siphonophora in all were present at thirty of the stations. 

 The fact that not many species were present at any one station in the Gulf of Aqaba has had a useful 

 systematic result, in that an Agalmid larva could be almost certainly identified as that of the species 

 Agalma okenii; the eudoxid of Chelophyes contorta could be definitely identified for the first time 

 owing to the absence of C. appendiculata ; and the eudoxid of Lensia hotspur and its posterior necto- 

 phore could be identified, because, apart from L. subtilis whose eudoxid is known, it was the only other 

 common species of Lensia present at the depth explored. The surface temperatures (21-22 C.) and 

 salinities (40-6-40-8 % ) were high, and no doubt the Siphonophores were at the lower limit of the 

 vertical hauls rather than at the surface. Unfortunately, hauls could not be made from depths below 

 180 m. or more specimens might have been taken. 



A sixth collection was made in the Red Sea off Port Sudan by M.Y. 'Manihine' in the winter of 

 1 950- 1. Three thousand eight hundred and thirty-seven specimens were removed from ten catches 

 and identified, providing almost the first records of Siphonophores from that area. 



A seventh collection, consisting of six bottles of plankton, was made in November 1951 with oblique 

 hauls from 200 m. or so to the surface in the Red Sea by 'Discovery II ' and was received in January 

 1952. This collection adds no species that were not taken there earlier by H.M.S. 'Weston' and by 

 M.Y. 'Manihine', and in fact does not contain specimens of seven species taken by them, but it 

 gives valuable corroborative evidence about the fauna of the area. Moie important, it has enabled 



