PLANKTONIC STUDIES. 569 
Although these negative conclusions 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 new tow net, which could be let down 
closed to a certain depth, and then opened and closed again. The 
merit of inventing such a closible 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 Pisani, first con- 
structed such a closible pelagic net or ‘“bathygraphical zone net;” and 
Naval Lieutenant Geetano Chierchia, who during the three years’ voyage 
of the Vettor Pisani 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 Kast 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 zoélogists. The 
collections brought back to Naples by the Vettor Pisani are, next to 
those of the Challenger, the most important materials from the region 
under consideration. 
A few faults which pertained 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 1886, made 
trials in the Gulf of Naples with the improved closible net which 
showed ‘‘a still more astonishing richness of pelagic animals in greater 
*The ‘‘tow nets” used by the Challenger were the ordinary Miiller’s net (or the 
‘‘fine pelagic net” of Joh. Miiller), around bag of Miiller gauze or silk mull, the 
mouth being kept open by a circular metallic ring. This ring is in ordinary pelagic 
fishing fastened to a handle 2 or 3 meters long (like the ordinary butterfly net). 
While the boat moves along, the opening of this net is held at the surface in such a 
way that the swimming animals are taken into the bag. They remain hanging 
in the bottom of this, while the water passes through the narrow meshes of the net. 
After a time the net is carefully inverted and the tow stutf (Au/ftrieb) 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 distance, correspond- 
ing to the desired depth. When Murray fastened such a tow net to the deep-sea 
sounding line or to the long line of the deep-sea dredge, he first obtained the inhabi- 
tants of the “intermediate ocean zones,” but he could not thereby avoid the objec- 
tion that, since this tow net always remained open, the contents might come from 
very different depths or even only from the surface. For in drawing up the open 
| tow net animals from the most different zones of depth might occasionally be taken in. 
