MUSEUM OF COMPARATIVE ZOOLOGY. 19 
modified as far as they relate to the Panamic District. According to 
the observations of the “ Albatross,” the specific gravities are too high 
off Panama. 
OBSERVATIONS ON THE PeLacic Fauna BY THE “CHALLENGER,” AND 
BY TH. STUDER IN THE “ GAZELLE.” 
Having always been more or less interested in pelagic faune, and 
having paid considerable attention to its vertical distribution during my 
earlier cruises in the “Blake,” I was naturally anxious to reconcile the 
conflicting statements and experiences of the naturalists of the “Chal- 
lenger” and “Gazelle” on one side, and my own observations on the 
other. 
The subsequent observations of Chierchia, of Chun, and of Hensen, and 
their discussion, have only increased the interest in the problem of the 
bathymetrical range of the pelagic fauna. Before giving an account of 
the work accomplished towards the solution cf the problem by the pres- 
ent trip of the “ Albatross,” I will rapidly give the results obtained since 
the ‘‘ Blake ” experiments. 
It should be remembered that Studer’s! statements were based en- 
tirely upon the assumption that the deep-sea Siphonophores, or their 
fragments, collected by him while in the “ Gazelle” from the sounding 
line, actually came from the depths to-which they were attached when 
the line reached the deck ; so that, for instance, a fragment of Siphono- 
phore coming up to the surface at the 650 fathom mark, or any other 
depth, indicated to Studer that the specimen was collected at that depth. 
From these observations Studer concluded that “auch die tiefen Was- 
serschichten nicht unbewohnt sind,” and that they did not come from 
higher levels, the tow-nets of the “Gazelle” having frequently been 
lowered to a depth of 200 fathoms without bringing up any Siphono- 
phores. He considers that the depth at which the Siphonophores oc- 
curred was a definite one, limited by the temperature,—a depth of from 
800 to 1,500 fathoms, with a temperature of 2° or 3° Centigrade. The 
experiments of the “Challenger,” on the other hand, consisted in sending 
open tow-nets down to various depths, and by a differentiation of the 
contents of the nets at different depths assuming that the changes in the 
catches were due to the several bathymetrical ranges of the species ob- 
tained. As the nets used by the “Challenger” were open tow-nets, all 
of which, on their way to the surface, passed through the upper and most 
1 Zeitschr. f. Wiss. Zool., XXXI., p. 1, 1878. 
