368 GEOGRAPHICAL DISTRIBUTION. 



among the Ellice group (Agassiz and Mayer, :02, p. 168). Chun ('97b) has 

 suggested that the scarcity of Physophores in the Tropical Atlantic in summer 

 observed by the "National," was a seasonal phenomenon, to be explained on the 

 assumption that at that time the species in question were passing through their 

 larval existence at considerable depths. Evidence in favor of this view is afforded 

 by the facts that the Siphonophore fauna collected by the "National" agreed 

 very closely with that observed by Chun ('88) himself at the Canaries from Sep- 

 tember to the last of December. It was only in winter that Forskalia, Agahna 

 etc. appeared on the surface. Furthermore, it has long been well known that 

 the Physophoras and Agalmids of the Mediterranean are seen regularly on the 

 surface only during the autumn and winter, and Chun ('87) has found that 

 during the suminer the larvae of Physophora are living there at considerable 

 depths. On the other hand the "Research" obtained no Physophore larvae 

 even in the deepest hauls, and the latter were made so frequently that these 

 organisms could hardly have escaped had they been as abundant as any of the 

 commoner Calycophores. Furthermore, I have been unable to disco\er that 

 any Forskalia, or Agalmid except Agalma okeni, occurs regularly anywhere on 

 the high seas far from land, either in the Atlantic or the Pacific, at any season. 

 The evidence afTorded by their occurrence suggests that these animals find their 

 most favorable environment in enclosed and sheltered basins, or near shore and 

 among islands, not in open sea. 



The explanation is, I believe, twofold. In the first place, as Chun has shown, 

 most of the long-stemmed forms are undoubtedly seasonal in their appearance. 

 During the rather extended period during which they pass through their lar\al 

 existence they may live at considerable depths, and in any case they are then 

 small, and easily overlooked. The second explanation, and as it seems to me 

 the more important one, rests on the anatomic structure of the species in question. 

 The only typically oceanic Agalmid, A. okeni, is of unusually short, stiff, non- 

 contractile "habitus," and its nectophores, bracts, siphons, etc., are very firmly 

 attached to the stem. Specimens of this species, like Physophoras and Antho- 

 physas, may even be removed from the water without injury. Such organisms 

 are well fitted to withstand buffetings by waves and currents. On the other 

 hand, Forskalias, and the long-stemmed Agalmids in general, are proverbially 

 delicate. They fall to pieces at the slightest touch, or even when the vessel in 

 which they are contained is jarred. (For a graphic account of such dissolution, 

 see Lens and Van Riemsdijk, : 08, p. 64.) Evidently during heavy weather such 

 animals are likely to be seriously damaged unless they can sink below the shallow 



