364 GEOGRAPHICAL DISTRIBUTIOxX. 



imhricata Haeckel, Desmophyes annectens Haeckel, and Rhodophysa corona 

 Haeckel, the only Indian species which are certainly not known from the Pacific 

 are Sphaeronectes princeps, Muggiaea huiieyi, and Lychnagalma uvaria. Until 

 we know more about the Pacific Apolemia and Epibulia it is impossible to say 

 definitely whether they are identical with the members of these genera from the 

 Indian Ocean. But there is nothing in the published descriptions of them by 

 Brandt ('35) to suggest that this is not the case. The agreement between the 

 two oceans is the more striking when we recall how few records of Indian Sipho- 

 nophores have yet been published. 



These facts of distribution show that so far as the Siphonophores are con- 

 cerned the Indian and Pacific oceans can not be separated. On the contrarj', 

 the entire tropical belt from the west coast of America on the one hand, to the 

 western side of the Indian Ocean, on the other, is a single uninterrupted faunal 

 zone. We have, as yet, no evidence of a distinctive Panamic fauna among 

 Siphonophores, indeed, it was not to be expected in a purely holoplanktonic 

 group. In their distribution the Siphonophores agree with the holoplanktonic 

 surface Medusae, and they differ correspondingly from the typical leptoline 

 forms, with long fixed, and short medusa stage, which, for distribution, are in 

 the same category as littoral organisms in general. For the latter, the Tropical 

 Pacific is "Separable into two more or less clearly defined areas; its western half 

 being closely connected to, if indeed at all separable from, the Malaysian 

 region . . . .and its eastern shores on the other hand having a close aflfinity to the 

 Gulf of Mexico and to the tropical Atlantic " (Bigelow, : 09a, p. 228) . And I may 

 forestall my forthcoming account of the Philippine Medusae collected by the 

 "Albatross" so far as to state that the data afforded by it is entirely in accord 

 with these generalizations. 



Comparison behueen the Species of the Indo-Pacific and the Atlantic regions. 



The intensive studies which have been made in the Mediterranean, among 

 the West Indies, and at the Canaries; the explorations of the "Plankton" 

 expedition, the investigations of the "Research" in the Bay of Biscay and the 

 numerous records from the coasts of North America and Europe, as well as from 

 scattered localities throughout the Atlantic, have given us a knowledge of its 

 Siphonophore fauna as nearly complete as that of any other purely pelagic 

 group of animals, though no doubt many gaps remain to be filled. Up to very 

 recently our knowledge of the Indo-Pacific members of the group was insufficient 

 for a comparative study of value between the representatives from the two 



