GEOGRAPHICAL DISTRIBUTION. 373 



we can say without hesitation that it certainly was not a characteristic member 

 of the plankton, yet at the same season it is approaching the zenith of its abun- 

 dance in the English Channel. And it as certainly was not present in the large 

 masses of West Indian plankton which I collected during Mr. Agassiz's Cruise 

 in the winter of 1907. It is likewise surprising that it has not been found in 

 the Mediterranean, though it may have been confused there with young Di-phyes 

 appendiculata. Another instance is the fact that Stephanomia rubra, so common 

 in the Mediterranean, has never been recorded from either side of the Tropical 

 Atlantic, although Bedot ('96) found it in the East Indies, at Amboina. The 

 occurrence of Diphyopsis mitra among the Canaries is extremely probable, 

 yet neither Haeckel nor Chun detected it there. On the other hand Muggiaea 

 kochii has not been found in the West Indian waters though it probably occurs 

 there. 



Even if no line can be drawn between the warm-water Siphoriophores of 

 the two sides of the Atlantic, they are not an altogether homogeneous group 

 geographically, for, as Chun ('97b) has pointed out, there is a considerable list of 

 species which are common in the Tropical Atlantic, but which do not occur in 

 the Mediterranean, though most of the Mediterranean Siphonophores are 

 known from the Atlantic. The species of Physophorae which were then known 

 from the Mediterranean only were Stephanomia rubra, Agalma clausi, and Lynchn- 

 agahna utricularia. But the first has since been found at Amboina; the second 

 may be, and the third almost certainly is identical with a form from the Indian 

 Ocean (p. 348, 349). In addition to these there are three Diphyids, Galeolaria 

 turgida, G. conoidea, smdG.ovata. But the first two are probably synonj'ms of 

 other species (p. 234, 235) and the third is a problematical form. And only one 

 species, Plutus cnidoporus Schneider, has been added to the list within recent 

 years. We may safely say, therefore, that it is doubtful whether any Sipho- 

 nophores are confined to the Mediterranean. 



On the other hand the following inhabitants of the Eastern Tropical Atlantic 

 which Chun mentioned as absent from the Mediterranean : — Diphyopsis dispar, 

 the Diphyes serrata group, Abylopsis eschscholtzi, Abyla trigona, Bassia bassensis, 

 Cuboides vitreus, Ceratocymba, Agalma okeni, Nectalia loligo, and Rhizophysa 

 eysenhardtii, have not been recorded from that sea even yet. To make the list 

 complete, we must add Amphicaryon acaule, Stephanophyes superba, and Anthe- 

 modes ordinata: and if the survey be extended to the western side of the Tropical 

 Atlantic, as it ought, for as we have seen the Siphonophores of the West Indies 

 correspond verj' closely to those of the Canaries, we may include Abyla leuckurtii, 



