SUPPLEMENT. 



13 



the so-called deep-sea Siphonophoroe, taken from the sounding-line by 

 Dr. Studer, on the 'Gazelle,' may have come, as I have so often observed 

 in the Caribbean, from any depth. I do not mean, of course, to deny 

 that there are deep-sea Medusae. The habit common to so many of our 

 Acalephs (Tima, yEquorea, Ptychogena, etc.) of swimming near the bottom 

 is well known; Dactylometra moves near the bottom, and Polyclonia 

 remains during the day turned up, with the disk downward, on the mud 

 bottom. I only wish to call attention to the uncertain methods adopted 

 for ascertaining at what depth they live. 



"As far as the pelagic fauna is concerned, those who have been in the 

 habit of collecting surface animals know full well that the least ripple 

 will send them below the reach of commotion; Miiller and Baur were 

 the first to adopt the use of a tow-net sunk below the surface to collect 

 pelagic animals when the water was disturbed. It seems natural to pre- 

 sume, as we have found from our experiments with the Sigsbee cylinder, 

 that this surface fauna only sinks out of reach of the disturbances of the 

 top, and does not extend downward to any great depth. The dependence 

 of all the pelagic forms upon food which is most abundant at the surface, 

 or near it, would naturally keep them where they found it in greatest 

 quantity. 



£> Of course, with the death and decomposition of the pelagic forms, 

 they sink to the bottom fast enough to form an important part of the food 

 supply of the deep-sea animals, as can easily be ascertained by examining 

 the intestines of the deep-water Echinoderms. The variety and abundance 

 of the pelagic fauna, and its importance as food for marine animals, are 

 as yet hardly realized. 



" One must have sailed through miles of Salpae with the associated 

 Crustacean. Annelid, and Mollusk larvae, the Acalephs, especially the 

 oceanic Siphonophores, the Pteropods and Heteropods, with the Radio- 

 larians, Globigerinae, and Algae, to form some idea how rich a field still 

 remains to be explored. The variety of the pelagic fauna in the course 

 of the Gulf Stream is probably not surpassed by that of any other part of 

 the ocean." 



