360 Wyville Thomson—General Ocean Circulation. 
live on the bottom, have come up from all depths, and at all 
depths the whole of the marine invertebrate classes are more 
or less fully represented. The abyssal fauna is of a somewhat 
ial character, differing from the fauna of shallower water 
in the relative proportions in which the different invertebrate 
types are represented. It is very uniform over an enormously 
extended area, and in this respect it fully confirms the antici- 
pations of the great Scandinavian naturalist, Lovén, communi- 
cated to this Association in the year 1844. It is a rich fauna, 
including many special genera and an enormous number of 
special species, of which we, of course, know as yet only a 
fraction; but I do not think I am going too far in saying that 
from the results of the Challenger expedition alone the number 
of known species in certain classes will be doubled. The rela- 
tions of the abyssal fauna to the faunz of the older Tertiary 
and the newer Mesozoic periods are much closer than are those 
of the faune of shallow water; I must admit, however, that 
these relations are not so close as I expected them to be—that 
hitherto we have found living only a very few representatives 
of groups which had been supposed to be extinct. 1, 
however, that until the zoological results of these later voyages, 
and es lang those of the Challenger, shall have been fully 
worked out, it would be premature to commit myself to any 
generalizations. ‘ 
I have thus attempted to give a brief outline of certain 
defensible general conclusions, based upon the results of recent 
eare me years ago, certain commercial enterprises, 
involving the laying of telegraph cables over the bed of the 
sea, proved that the extreme depths of the ocean were not 1nac- 
cessible. This somewhat unexpected experience soon resulted 
in many attempts, on the part of those interested in the exten- 
sion of the boundaries of knowledge, to use what machinery 
they then possessed to determine the condition of the hitherto 
unknown region. This first step was naturally followed by a 
development of all appliances and methods bearing upon the 
special line of research ; and within the last decade the advance 
of knowledge of all matters bearing upon the physical goon 
phy of the sea has been confusingly rapid—so much so, that 
at this moment the accumulation of new material has far out- 
iad, the power of combining and digesting and methodizing 
. This difficulty is greatly increased by the extreme com- 
pea of the questions, both physical and geological, which 
ave arisen. Steady progress is, however, being made 12 
both directions, and I trust that in a few years our ideas as 
to the condition of the depth of the sea may be as definite as 
they are with regard to regions to which we have long had 
ready access, 
