232 THE MEDUSAE. 



have been overlooked in much of the general discussion of the range of the 

 bathypelagic fauna. 



The captures of intermediate Medusae recorded by the recent Euro- 

 pean deep-sea expeditions have been for the most part from comparatively 

 deep hauls, — usually from below 500 fathoms, and often from very much 

 greater depths. From less than 300 fathoms very few intermediate Me- 

 dusae are recorded either by the "Valdivia" or "Siboga" expeditions, or by 

 those of the " Princess Alice." It seems that this absence is to be explained 

 largely by the fact that on all these expeditions but few comparatively 

 shallow hauls, except from such trivial depths as 20 or 30 fathoms, were 

 made with nets of a type fitted for the capture of large organisms. In esti- 

 mating the value of such negative evidence it must be borne in mind that 

 the fine-meshed Plankton net, especially after being used a few times, is 

 admirably calculated to miss all large specimens when in use at the speed 

 of a steamer under way. We cannot, then, interpret the scarcity of records 

 from these expeditions of intermediate Medusae from the upper 300 fathoms 

 as indicating absence of these organisms in that zone. On the contrary, 

 there is good evidence that they not only occur, but are abundant between 

 300 fathoms and the surface. Thus the few captures of intermediate 

 Medusae in open nets on the "Research" expedition are all from mode- 

 rate depths, — the records being, Colobonema from 250 fathoms to surface ; 

 Homoeonema plati/gonon, 100 fathoms to surface, 200 to surface, 250 to 

 surface, and 350 to surface; and of Periphylla, from 350 fathoms to the 

 surface (Browne, : 06). And even more positive evidence to the same effect 

 is afforded by the present collection. 



During the expeditions of the "Albatross," particularly that of 1904-05, 

 the method of towing has been to make frequent hauls from 300 fathoms to 

 the surface, and occasional deeper hauls, which, together with the numerous 

 trawl hauls, might be expected to reveal pelagic organisms confined to the 

 region below 300 fathoms. The results from this method of collection were 

 particularly positive and instructive on the Expedition of 1904-05. During 

 this trip intermediate Medusae were taken in forty hauls at thirty-five sta- 

 tions, the depths being : — at twenty-three stations, 300 fathoms to surface ; 

 two stations, 400 fathoms to surface ; one station, 600 fathoms to surface ; 

 one station, 800 fathoms to surface ; and at nine stations in the trawl. 



A significant feature of the case is that in every instance in which a 300 

 fathom haul was made at the same station where intermediate Medusae 



