248 STALK-F.YED CRUSTACEA. 



complexion of the deep-sea fauna, attain their maximum development within 

 the tropics. 



So few pelagic or surface species are included in this Report, that a dis- 

 cussion of the distribution of the pelagic fauna Avould be out of place here. 

 The experiments in towing at various depths with the self-closing Tanner 

 net proved beyond question that the pelagic fauna may sink during the heat 

 of the day, or under other adverse conditions of the sui'face, to a depth of 100 

 to 250 flithoms.* 



"With regard to the vertical distribution of the species that come up in 

 the dredge or trawl, it may be taken for granted that the ambulatory forms, 

 whose structure fits them only for life on the ocean floor, really come from 

 the bottom. But many natatory species are also captured when dredging at 

 great depths. Such are the swimming prawns belonging to the family Hop- 

 lophoridae, certain Pasiphaeiidoe, Peneida3, and Sergestida3, and the deep-sea 

 Schizopods. It is evident that these may never have come from the bottom, 

 but that they may have entered the open trawl on its way up to the surface. 

 The absence or rarity of some of these forms in collections made at or near 

 the surface, taken in connection with structure and color of the animals them- 

 selves, signifies that they normally dwell at a great depth. Tlie experiments 

 with the Tanner net towed at great depths, within 100 fathoms or so of the 

 bottom, are of great interest in this connection. At Hydr. Station 2619, the 

 net was towed for sixteen minutes at a depth of 1000 fathoms (100-482 

 fathoms above the bottom)- A specimen o^ Eucopia and a violet colored Am- 

 phipod came up in the lower part of the net, which had been closed at 

 1000 fathoms. At Ilydr. Station 2627 (1832 fathoms) the net was towed at 

 1740-1770 fathoms for twenty minutes, but nothing was captured in the 

 closed part of the net. In the upper part of the net, which came up open 

 all the way from 1740 fathoms to the surface, were four specimens of 

 Eucopia. A .similar trial at Station 3436 failed througli the water shoal- 

 ing and the net dragging the bottom. At Station 2637 (Gulf of Cali- 

 fornia, 773 fathoms) the net was towed at 70 fathoms above the bottom, 

 but in this case the net came up open to the surface, bringing with it two 

 deep-sea Schizopods, — Eucopia and the eyeless retalophthahnus. Again, at 

 St-ition 2638, in the Gulf of California, the net was towed at a depth vavy- 



• See A. Agassiz in Bull. Mus. Comp. Zool., XXIII. 48-5G, 1892, and Oriniann in Bull. Mus. Comp. 

 Zool, XXV. 108-110, 1894. 



