MATERIAL AND METHODS n 



bench that the drawing could be moved about underneath it. Thus by movements of the specimen 

 on the stage, of the stage on the track, and of the drawing, it was possible to make large drawings, 

 1 8 in. or more across. 



Preserved specimens were stained lightly with Delafield's haematoxyl n and photographed in 

 formalin. To obtain the view of the ostium of the nectophore of Abyla tottoni Sears (PL IX, fig. 4) 

 the specimen was held in a vertical glass tube in a vessel of formalin. As well as light from the top, 

 some was reflected upwards through the specimen. Maresearsia praeclara (Pis. VI and VII) was 

 photographed with a Leitz 400 mm. Milar lens. The photomicrographs 4 and 5 of PI. IV were 

 made by Mr M. G. Sawyers, principal photographer, with a 3 in. Holos lens, and the others 

 (unless otherwise stated) were made by Mr J. V. Brown of the Museum Staff, with a Leitz Sumnar 

 12 cm. lens. 



Acknowledgements. I am grateful to Dr W. J. Rees for having read the draft of this report, and to 

 Dr Helene Bargmann of the National Institute of Oceanography for a great deal of help. 



SIPHONOPHORE FAUNA OF THE RED SEA 



This report gives, for the first time, 1 a record of the Siphonophores which live in the Red Sea and in the 

 Gulf of Aqaba. These are areas about whose Siphonophores we previously knew practically nothing. 

 It is therefore satisfactory to be able to include in this work on the species from the Indian Ocean, 

 material collected from these two localities. This fauna, to judge from the material so far available, 

 does not include the following species found elsewhere in the Indian Ocean: 



Porpita umbella Chnniphyes multidentata A. leuckartii 



(?) Physalia physalis Clausophyes ovata Chelophyes appendiculata 



Physophora hydrostatica Sulculeolaria monoica Eudoxoides mitra 



Rosacea cymbiformis [Galetta] S. biloba E. spiralis 



R. plicata [G.] S. turgida Lensia achilles 



Hippopodius hippopus Dimophyes arctica L. campanella 



Vogtia glabra Diphyes bojani L. conoidea 



V. pentacantha Abyla haeckeli L. cossack 



V. serrata A. trigona (sp. aff.) L. multicristata 



Bigelow & Sears (1937) showed that there was a paucity of siphonophore species in the Medi- 

 terranean as compared with the Atlantic beyond, and noted that two of the reasons for this probably 

 were (a) the excluding action of the deep outflow over the sill upon species which lived below that level, 

 (b) the rather high minimum temperature (12-13 C.) of the Mediterranean deep water. 



There appears to be an even greater paucity of siphonophore species in the Red Sea as compared 

 with the Indian Ocean outside. Here again the deep outflow over the sill at the southern entrance 

 of the Red Sea probably has an excluding action on deeper-water species, and the even higher 

 (21-5-22° C.) minimum temperature of the Red Sea deep water would be unbearable for such species, 

 even if they entered. 



Sverdrup, Johnson & Fleming (1946), summarizing the work of Thompson and others on the water 

 masses of the Indian Ocean, say that the entire basin of the Red Sea below sill depth (100 m.) is filled 

 in winter with water which has a salinity of from 40-5 to 4i-o% , and a temperature between 21-5° and 

 22° C. : and that it has a very low oxygen content, less than 1 ml./L. in summer, a little more than 

 2 ml./L. at the end of the winter. The maximum surface temperature in summer is about 30° C. and 



1 Schneider (1898, p. 120) mentioned that Steindachner, scientific leader of the 'Pola' Expedition had handed over to 

 him two Siphonophores from the Red Sea, now known as Agalma okenii and (possibly) Melophysa melo. 



