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Vol. IX, No. 1.] Sponges of the Lake of Tiberias. 75. 
[N.S.] 
It is easy to see that a sponge living in a warm climate in 
a lake in which a considerable depth of water is maintained 
throughout the il has not the same need for the production 
gemmules as one from a small pond or stream that is liable 
to be dried up or oi solid. Marshall has advanced the 
view that an important function of the gemmule-spicules is that 
of weighting the gemmules, in order that they may not float 
away too readily. If so, it is not — that in species in 
which the gemmules are adherent their microscleres should 
disappear, and as the main See of the pneumatic coat is 
that of oes the gemmules to float, this coi might also be 
expected, on d@ priori grounds, to be eliminated in the same 
circumstances, just as the eyes of cavernicolous animals are 
eliminated in the dark. 
mbryos were found in all species of Galilean sponges 
examined in October, proving that sexual solace as well 
as vegetative growth is vigorous at that time of y 
As Cortispongilla barroisi is the most aoe ‘specialized 
species oa the sponge-fauna described in this paper, it will be 
iscuss the a ee of its peculiarities. 
itl 
for the production of a skeletal cortex and for the possession 
of a well-defined and almost symmetrical central cavity. (It 
would be misleading to call the latter a gastral cavity, for 
there is no evidence that it is homologous with the gastral 
sponges that live in still water. It is almost obliterated in speci- 
mens attached to bushes the supra-aquatic parts of which are 
agitated by the wind, its place being taken in this case by super- 
ficial branching channels, and also in races from south-western 
India and eastern Europe as to the biology of which we are igno- 
rant. The only freshwater sponge in which a cavity is found 
comparable to that of C. barroisi in regularity is Pachydictyum 
osum from Celebes,” in which the relative size and the actual 
ene of the cavity are greater than in the Galilean species. 
ig was found attached to the shells of living Gastro- 
pods in a ake in Celebes. The production of a cavity of the 
kind, which is one with the presence of a large circular 
osculum, is apparently a provision to assist in the elimination 
of mud or sand pre into the system through the pores, the 
exhalent channels being strong enough to keep the osculum 
I have noticed that if Spongilla proliferens is kept alive 
in an aquarium, the number of oscula (and consequently tl oP 
. As. Soc. Bengal, 1906, pl. i 
: Wallac itera Arch. f. eho ty a, ok vi, fig. 3 (1901). 
