150 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 
the cruise.” The same is true of the Wilkes plankton, although the 
statement does not appear in Dana’s record. In the Carnegie expedi- 
tion three horizontal tows were taken at each station, one at the 
surface, one at a depth of 50 meters, and the third at a depth of 100 
meters (only one vertical haul, from 1,000 fathoms to the surface, 
was made during the entire cruise). Our knowledge of the oceanic 
plankton, therefore, is almost entirely confined to what is found at 
the surface, and we know practically nothing of the copepods living 
in the depths. 
The excellent Monaco monograph by Sars (cf. p. 144) bears the title 
“Copépodes particuligrement bathypélagiques.” This could well be 
taken as contradictory unless it be explained that the vertical hauls 
(86 percent) yielded four times as much plankton as the surface 
tows (64 percent), with a very pronounced superiority in the variety 
of species. Lacking devices by which the nets employed couid be 
opened just before a vertical haul was made and be closed immediately 
upon its completion, the nets would of course function as open nets 
while being lowered to the required depth, in the course of their 
upward passage for the duration of the haul, as well as up to and in- 
cluding the surface itself. Thus the depth at which any specimen 
entered the net can never be established. The mere presence of a 
particular species within a net after a vertical haul would not be evi- 
dence that it is bathypelagic. Only if it is found in several vertical 
hauls and not at all in the surface tows could negative evidence be 
claimed. It is upon such evidence, which is excellent as long as it re- 
mains true, that the Monaco specimens were claimed to be bathypelagic. 
But there is always a menace to such negative proof in the possible 
future discovery in surface tows of a species declared to be bathype- 
lagic (cf. Gaetanus miles, p. 232). 
As to the relative abundance of the copepod plankton at the surface 
or in the depths we find much interesting evidence. In the Siboga 
plankton 65 surface tows captured an average of 35 species apiece, 
while 15 vertical hauls averaged 69.1 species, and one of them yielded 
131 species. In the Monaco plankton 76 of the surface tows yielded 
but a single species apiece, and for the whole 210 tows the average 
was only 3.60 species. On the other hand, the 136 vertical hauls 
contained an average of 21.70 species and one of them yielded 84 
species. In the Carnegie plankton, with one exception, there were 
no vertical hauls, but simultaneous horizontal tows were taken at three 
depths with a slight difference in favor of the deepest tow. In the 
Albatross plankton 152 surface tows contained an average of 16 
species, while 180 vertical tows yielded an average of 20 species. 
So much then for the past and the present of the plankton through 
nearly a hundred years, and now what of the future? A good start 
