8 DISCOVERY REPORTS 



and in their arrangement on the oozooid, all have very definite characters. As a rule it is far more 

 worth while to figure accurately the details of these buds than to attempt to give a sketchy figure or 

 description of the whole animal. Indeed, it is a most exacting task to make a figure of a live 

 Siphonophore such as a Forskalia or Apolemia. Most of them are transparent, extremely complex 

 in shape, and very active in movement as a whole, and in expansion and contraction of the stem, 

 tentacles and nectophores. In addition to these difficulties, specimens as a rule quickly become 

 moribund in captivity. 



Much of the literature is full of names that only with grave doubt can be referred to zoological 

 concepts. For many years now I have been occupied with the laborious task of picking out hundreds 

 of thousands of fragmentary specimens from plankton samples and of trying to form some idea of 

 how many species are represented, and then attempting to apply old specific names and, where 

 none are available, giving new ones. Gradually specialists are building on the foundations laid by 

 their illustrious predecessors and on their own early work, and are beginning to recognize the various 

 species. The greatest stimulus to progress is given by field work, but unfortunately the opportunities 

 afforded to me for this have been very limited. 



The best known and most easily identifiable Siphonophores are perhaps those of the Mediterranean, 

 a region where so much of the pioneer work on the group was done, and a region where many are 

 often easily accessible at the surface, as long as the sea is calm and sea-temperature does not exceed 

 2i° C. The least well known are those of the Indian Ocean, for which reason this report has been 

 prepared with no little labour. 



Many species are difficult to take with tow-nets, except in fragments, and it is probable that manv 

 species of a particular fauna of Siphonophores will always be missed by the nets. As an illustration of 

 this fact, in intensive tow-netting campaigns from 1908 to 19 10 in the Mediterranean, the 'Thor' 

 missed not only all the common Physonects like Agalma, ' Stephanomia ', Forskalia and Apolemia, 

 but also such abundant species as Muggiaea kochii and Lensia subtilis. Another explanation for the 

 absence from ' Thor ' catches of the last two species is that they may be neritic forms. 



MATERIAL AND METHODS 

 Our knowledge of the Siphonophora of the Indian Ocean was summarized by E. T. Browne (1926) 

 in his report on thirty-six species taken on the ' Sealark ' Expedition by Stanley Gardiner. ' Sealark ' 

 ranged over the banks and slopes of the Chagos Archipelago, the Seychelles and the Mascarene 

 Islands, in the tropical zone during the months May to October. The Siphonophores collected by 

 'Dana II' in the 1928-30 cruise are being worked out by Dr Mary Sears. Jesperson (1935) gives 

 a summarized list of stations showing that a large number of plankton hauls were made in the Indian 

 Ocean from the north point of Sumatra across to Ceylon and thence via the Seychelles to the north 

 point of Madagascar and to Mombasa. Changing southwards, the route then passed through the 

 Mozambique channel to Durban, thereafter following the coast-line down to Cape Town. The 

 macroplankton on the line Ceylon-Madagascar-Mombasa appears to have been much richer than that 

 on the stretch through the Mozambique channel down to Cape Town. 



Dr Sears's ' revision of the Abylinae ', published since this report went to press, contains records of 

 Indian Ocean specimens of Abyla bicarinata Moser, A. brownia Sears (sp.n.), A. carina Haeckel 

 [=A. trigona Q. & G.], A. haeckeli L. & van R., A. ingeborgae Sears (sp.n.), A. schmidti Sears (sp.n.), 

 A. trigona Q. & G., Ceratocymba dentata Bigelow and C. leuckartii Huxley. 



From September 1933 to May 1934, the John Murray Expedition with the ' Mabahiss ' was working 

 principally in the open West Tropical Indian Ocean, in the Somali and Arabian Basins, and brought 

 back thirty-nine species of Siphonophores. 



