PLANKTONIC STUDIES. 619 
with life” (p. 218). This astonishing wealth of plankton was observed 
in the whole breadth of the Atlantie tropical zone in August and Sep- 
tember, 1873; but it was not less than that passed by the Challenger 
on her return in Mareh and April, 1876, in the eastern part of the same 
region, between Tristan d’Acunha and Cape Verde. ‘ When the water 
was calm, an extraordinary superabundance of pelagic life appeared at 
the surface. Oscillatorivw covered the sea for miles, and vast quantities 
of Radiolaria (Collozoun) filled the nets” (p. 930). With those and 
other accounts by the Challenger, those of the Vettor Pisani quite agree. 
“ The zone of equatorial calms is out of all proportion rich in organic life. 
Sometimes the water seems coagulated, jelly-like, even to the touch. 
It is impossible to describe the quantities of variously colored forms” 
(8, p. 31). Chierchia enthusiastically describes the wonderful spectacle 
which the luminous ocean furnishes at night—“‘a sea of light which ex- 
tends to the whole horizon” (pp. 32, 53, etc.). The numerous plankton 
samples which I myself have investigated from the Atlantic tropical 
zone Show for the most part an extraordinarily rich composition, par- 
ticularly those between Ascension and the Canary Islands (Challenger 
stations 345 to 353), above all the two equatorial stations 347 and 348, 
which, like the Canary currents, which I studied for three months at 
Lanzarote, whose fabulous wealth I have already mentioned, also belong 
to the region of the tropical trades-drift. 
The quantity and wealth of forms of the plankton in the tropical 
zone of the Pacifie Ocean is not less than in the tropical region of the 
Atlantic and Indian oceans. In the most diverse parts of this region 
the Challenger sailed through “thick banks of pelagic animals.” 
Between the New Hebrides and New Guinea “the surface of the water 
and its deeper levels swarmed with life. All the common tropical 
forms were found in great abundance. The list of genera of animals 
was about the same as in the Atlantic tropical region (pp. 218, 219), but 
it showed considerable difference in the relative abundance of 8pecies” 
(6, p. 521). Among the Philippines the water showed “a quite uncom- 
mon quantity and variety of oceanic surface animals” (p. 662). On 
the voyage froin the Admiralty Islands to Japan the oceanic “fauna 
and flora of the surface was everywhere especially rich and varied. 
In the neighborhood of the equatorial countercurrents, between the 
equator and the Carolines, pelagic foraminifera and mollusks were 
taken in such quantities in the surface net that they surpassed all 
earlier observations,” ete. (p. 738). On the voyage through the central 
part of the tropical Pacific, from Honolulu to Tahitizbetween 20° N. 
lat., and 20° S. lat., “the catch of the tow net was everywhere very 
Yich. The superabundance of organic life in the equatorial current and 
countercurrent is very noticeable, as well with reference to the number of 
species as of individuals” (p. 776). From this wonderfully rich region, 
which of all parts of the tropical ocean is farthest removed from alb 
continents, came the absolutely richest plankton samples which I have 
