MUSEUM OF COMPARATIVE ZOOLOGY. 55 
from the presence of numbers of brachyuran larvee, such as we had 
already found on the previous day in our surface haul. We obtained 
Periphylla, Stomobrachium, the new genus of Bougainvillia, bells of 
Diphyes and other Siphonophores, Doliolum, several species of Ptero- 
pods, Sagittz, Ostracods, Copepods, Hyperiade, Schizopods, Penzids, 
and a few species of pelagic fishes. 
On the 23d of April, a few hours before reaching Guaymas, we made 
one more attempt with the Tanner tow-net, Hy. Station 2638, at a 
depth of 622 fathoms, sending the net to be towed for about fifteen 
minutes, at a depth of from 500 to 570 fathoms. We found in this 
case in the bottom part of the net, which came up tightly closed, a 
Scopelus, a red Penzid, and a Hyalea, while the upper open part of 
the net contained the same surface species we had obtained in the sur- 
face tow-net on other occasions, such as Squilla larvee, Ostracods, Dolio- 
lum, Euphausiz, and Pteropods. 
Our experience in the Gulf of California with the Tanner self-closing 
net would seem to indicate that in a comparatively closed sea, at a 
small distance from the land, there may be a mixture of the surface 
species with the free-swimming deep-sea bottom species, a condition of 
things which certainly does not exist at sea in deep water, in an oceanic 
basin at a great distance from shore, where the surface pelagic fauna 
only descends to a comparatively small depth, i. e. about 200 fathoms, 
the limits of the depth at which light and heat produce any consid- 
erable variation in the physical conditions of the water. The marked 
diminution in the number of species below 200 fathoms agrees fairly 
with the results of the “ National” expedition. 
The other experiments with the Tanner net, made in an oceanic ba- 
sin on the way to Acapulco from the Galapagos, and to the Galapagos 
from Cape San Francisco, seem to prove conclusively that in the open 
sea, even when close to the land, the surface pelagic fauna does not 
descend far beyond a depth of 200 fathoms, and that there is no in- 
termediate pelagic fauna living between that depth and the bottom, 
and that even the free-swimming bottom species do not rise to any 
great distance, as we found no trace of anything within 60 fathoms from 
the bottom where it had been fairly populated. 
The first experiments of Chun regarding the distribution of the 
pelagic fauna were made in the Mediterranean, within a comparatively 
short distance from the shore, and in a closed basin having, as is 
well known, special physical conditions, its temperature to its greatest 
depths being considerably higher than the temperature of oceanic basins 
