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Vol. IX, No. 1.] Sponges of the Lake of Tiberias. 73 
[N.S.] 
this species I obtained were, moreover, actually in ‘the Jordan 
just after it had left the lake, and when i n flood the stream 
must flow with great strength at this point. 
The case of the sponges of the Jordan channel in the lake 
is not quite the same. They cannot be affected by storms to 
but that there is a considerable current, perhaps increased in 
wet weather, in that part of the lake in which they live, is 
proved by the fact that the bottom is there devoid of fine silt 
and covered with coarse grit and small stones. Only a very 
small part of the channel has yet been explored, but, so the as is 
at present known, Cortispongilla barroisi is confined to an area 
of not more than two square miles. This was found to be the 
case both by Barrois, whose investigations were made in om 
d by myself in October. N. aste er, on the other hand, 
tural peculiarities of C. barroisi and their biological significance 
I shall deal presently, but it is noteworthy that N. aster is by 
far the most friable of the Potamolepidinae known from the 
lake. 
A most important question both from a taxonomic and a 
biological point of view is that of the production or non-pro- 
duction of gemmules by the Potamolepidinae. The evidence 
Galilean species that gemmules are at any rate not habitually 
produced, and we know that in a few species (Nudospongilla 
caggini, N. moorei and N. Be pp a: of the sub-family these 
bodies are sometimes fou I have found them also in a 
ar of Veluspa Pa from Lake Baikal. In all these 
sponges they are devoid not only of microscleres but also of 
asta coat and foramina. In Spongilla (Stratospongilla) 
clementis from the Philippines, the structure of which closely 
resembles that of Nudospongilla generally, and especially that 
of the type-species NV. coggini, the gemmules are few in number 
d bear remarkably attenuated microscleres ; while imper- 
fect development of the pneumatic coat is a common feature 
of the species of Stratospongilla, a Ithough in one species (N. 
bombayensis) it is less degenerate in a variety or local race 
(pneumatica) than it is in the typical form. The disappear- 
ance of the gemmule is therefore not a character of so funda- 
oe a nature as might appear at first sight to to be the case 
e find some species in which it has lost the elaboration 
diacterate of the Spongiltidas as a family, and others in 
which it has apparently been suppressed altogethe r. 
The evidence that the latter statement is true lies, so far 
as the sponges of the Lake of Tiberias are concerned, in the 
