REPORT ON THE TETRACTINELLTDA. 
381 
DISCUSSION OF THE DISTRIBUTION OF THE TETRACTINELLIDA. 
The data at our disposal are as yet altogether inadequate for an independent and 
complete discussion of the problem of the distribution of the Tetractinellida ; the number 
of recorded species is certainly large, but far from being large enough, and though they 
have been gathered from many localities, yet there are wide areas from which not a 
single species is known. But even were it otherwise, it would probably be scarcely 
prudent to undertake the investigation of the question of distributional areas on the 
facts presented b}^ a single group of sponges, and that not a very large one. 
At the same time I may be permitted to point out certain coincidences and to 
offer some suggestions. 
In the first place, as a glance at the appended map will show, all the stations from 
which Tetractinellida have been obtained are situated, quite irrespective of depth, at no 
great distance from land. The course of the Challenger is indicated by a long train of 
dredgings, unsuccessful as regards the capture of Tetractinellids, till the approach of 
land, and then the red circle indicative of a successful haul at once appears. This would 
not be a fact of any special significance if the Tetractinellida, like the Calcarea and 
Ceratosa, were exclusively shallow- water forms, but it acquires great interest when we 
find that characteristically deep-water forms, like the species of the genus Thenea, are 
similarly confined to the vicinity of land ; these species have been obtained nine times 
from depths between 1000 and 2000 fathoms, but in every instance they were found 
near the shores of some continent or island. Out of one hundred and forty-four dredgings 
between 1000 and 2000 fathoms, the Challenger eight times obtained species of Thenea 
near land, but not one at any great distance from it. In the case of the Hexactinellida, 
Schulze states that they were indeed found in the middle of the great oceans, but 
“ generally speaking the abundance of species was least at a distance from the mainland, 
and in the middle of the great oceanic basins, than in the neighbourhood of the continent 
or island groups.” The Monaxonida in the same way cling to the land, though with 
more frequent exceptions than in the case of the Tetractinellida ; in the North Atlantic 
the statement is true without an exception ; in the South Atlantic, with one, as at 
Station 332, where, remote from land, from a depth of 2200 fathoms, a single species 
was obtained ; in the Indian Antarctic it is likewise true with a single exception, that 
of Station 157, which yielded one species from a depth of 1500 fathoms ; the Pacific 
furnishes four exceptions, three stations at a considerable distance from land yielded 
each one species from depths of between 2000 and 3000 fathoms, these are Station 
241, 246, and 248 ; and a fourth. Station 291, two species from a depth of 2250 fathoms. 
Stations 241, 246, and 248 ought perhaps not to be reckoned as exceptions, since 
they are within 300 miles of coral reefs, and I have regarded in the case of Thenea 
