PLANKTONIC STUDIES. 569 



Although these negative coucUisious from the so-called " exact ex- 

 periments" of Agassiz are contradicted by the foregoing results of the 

 Challenger investigator, yet against the latter, with some show of right, 

 Agassiz might have raised the objection that the "tow net" used could 

 establish no safe conclusion.* This objection could only be finally 

 removed by the construction of a u"ew tow net, which could be let down 

 closed to a certain depth, and then opened and closed again. The 

 merit of inventing such a (dosible net, and of the immediate successful 

 use of it, belongs to two distinguished Italian naval officers: G. Pal- 

 umbo, commander of the Italian war corvette Vettor Plsani, first con- 

 structed such a closible pelagic net or "bathygraphical zone net;" and 

 Naval Lieutenant Gsetauo Chierchia, who during the three years' voyage 

 of the Vettor Fisani around the world made a very valuable collection 

 of pelagic animals, used the new closible net with fine results, even at 

 a depth of upwards of 4,000 meters (8, p. 83). 



Chierchia's first trial with this "deep-sea closible net" was June 5, 

 1884, in the East Pacific Ocean, directly under the equator, 15° west of 

 the Galapagos Islands. Fourteen days later, June 19, midway between 

 the Galapagos and the Sandwich Islands, this closible net was sunk to 

 4,000 meters. In this and in many other trials these Italian naval 

 officers captured an astonishing wealth of new and interesting zonary 

 animals, whose description has for a long time busied zoologists. The 

 collections brought back to ]Srai)les by the Vettor Plsani are, next to 

 those of the ChaUem/er, the most important materials from the region 

 under consideratitm. 



A few faults which i)ertained to Palumbo's net were soon done away 

 with by improvements, for which we are indebted to the engineer Peter- 

 sen and to Prof, Carl Chun, of Breslau. The latter, in 1880, made 

 trials in the Gulf of Xaples with the improved closible net which 

 showed "a still more astonishing richness of pelagic animals in greater 



* The " tow nets " used hy the Challenger -were the ordiuary Miiller's net (or the 

 " fine pelagic net" of Joli. Miiller), a round hag of Miiller gauze or silk mull, the 

 mouth heiug kept open hy a cir(;ular metallic ring. This ring is iu ordinary pelagic 

 fishing fastened to a handle 2 or 3 meters long (like the ordinary hutterfly net). 

 Whill^ the hoat moves along, the opening of this net is held at the surface in such a 

 way that the swimmiug animals are taken into the l)ag. They remain hanging 

 in the bottom of this, while the water passes through the narrow meshes of the net. 

 After a time tiie net is carefully inverted and the tow stuff (Auftrieb) is emptied 

 into a glass vessel filled with sea water. If one wishes to fish below the surface, 

 the ring of .the net is fastened by means of three strings, equally distant from one 

 another, which at a point (about 1 meter distant from the opening of the net) are 

 joined to a longer line which is sunk by weights to a definite distau(;e, correspond- 

 ing to the desired depth. When Murray fastened such a tow uvt to the deep-sea 

 sounding line or to the long line of the deep-sea dredge, he first o)»taint'd the inhabi- 

 tants of the " intermediate ocean zones," hut he could not thereby avoid the objec- 

 tion that, since this tow net always remained open, the contents might come from 

 very difTerent depths or even only from the surface. For in drawing up the open 

 tow net animals from the most diflerent zones of depth might occasionally be taken in. 



