GEOGRAPHICAL DISTRIBUTION. 365 



oceans. But the collections made by the "Siboga" and by the "Albatross" 

 are so extensive that such a comparison is now possible and timely. 



The most important question to answer is whether these purely pelagic 

 organisms support the thesis of the uniformity of the oceanic plankton in tropical 

 and subtropical regions throughout the globe. The table of species (p. 383) 

 shows that out of fifty Calycophorae, twenty-three occur both in the Atlantic 

 and in the Indo-Pacific; twelve are as yet recorded only from the Atlantic, 

 fifteen from the Indo-Pacific. And I may point out that in most cases my 

 identification of Pacific with Atlantic Calycophores rests not only on published 

 descriptions of the latter, but on studies of series from both oceans. At the 

 first glance these numbers suggest a remarkably close resemblance in the Sipho- 

 nophore faunae. And the unity becomes even more complete when we analyze 

 the status of the exclusively Atlantic and Indo-Pacific species. One of the 

 Atlantic forms, Galeolaria ovata Kefferstein and Ehlers, is problematical, and 

 therefore can not be used one way or the other. One, Diphyopsis hispaniana 

 Mayer (p. 344) is of doubtful validity. The Diphyes steenstrupi-serrata group 

 is represented in the Pacific by an ally so close that it is very doubtful whether 

 it is distinct. .\nd the same is true of Galeolaria biloba. Two species, Necto- 

 pyramis ihetis Bigelow and Stephanophyes superba Chun,, are known from only 

 one or two records each, and may, not improbably, come to light in the Pacific 

 later. One, Diphyes arctica Chun, is an Aj'ctic and Subarctic species and 

 therefore would not be expected in the warmer zones of the Indo-Pacific, which 

 are the only parts of that oceanic region from which any Siphonophores are 

 known. This leaves only seven warm water Atlantic species which are certainly 

 not yet known from the Indian Ocean, or from the Pacific. These are, Sphaer- 

 onectes irregularis, Doromasia picta, Ncctopyramis ihetis, Stephanophyes superba, 

 Diphyes subtilis, Vogtia pentacantha, and probably Galeolaria truncata. But con- 

 sidering how few studies of the Siphonophores of the Indo-Pacific have been 

 made it is not at all improbable that some of these will be found there. 



Two of the peculiarly Indo-Pacific species, Desmalia imbricata Haeckel and 

 Desmophyes annectens Haeckel, are problematical. It has been suggested that 

 they belong to Pray a cymbiformis and to Rosacea plicata, but they are recognized 

 here provisionally. Two species, Sphaeronectes princeps Haeckel and Muggiaea 

 huxleyi Haeckel, are known from only one record each; their validity has been 

 questioned. Galeolaria australis and Diphyes bojani are represented in the 

 Atlantic by allies so close that it is doubtful whether they are distinct. This 

 leaves only Nedopyramis diomedeae Bigelow, Nectrodroma dubia Quoy and Gaim- 



