398 Dr, W. Marshall on new Stliceous Sponyes. 
This much is certain. The formation of capsuled winter- 
germs is by no means an exclusive peculiarity of the fresh- 
water sponges, in which it does not even universally occur 5 
it occurs in exactly the same manner in such very different 
animals as the Bryozoa, to say nothing of other analogous 
cases. But if so close a similarity is possible between the 
statoblasts of the latter and the gemmules of the former, are 
these gemmules really of decisive significance in the settle- 
ment of the question of the relationships of the freshwater 
sponges? Hardly; any more than the development of wti- 
‘ating organs can be decisive in judging of the relationships 
of the lower aquatic animals. What Bryozoa and sponges 
could acquire independently of each other, members of one 
and the same order can acquire sud generis, ‘without any direct 
relationship between them being thereby demonstrated. 
If, then, the different freshwater sponges agree in the struc- 
ture of the skeleton, not only among themselves, but also in 
general with the majority of the marine siliceous sponges ; If, 
further, as any one will admit, their common occurrence fresh 
water is, according to all analogy, of no value whatever in the 
elucidation of their relationships; and, finally, if structures 
pertectly analogous with the vemmules can be acquired by 
similar adaptation by such perfectly different animals as 
Bryozoa, upon what is the tee et of a monophyletic 
origin for the so-called Spongille really based? ‘This 
seems to me a question that may well be raised. It will 
justly be required of me that I should give the reasons that 
lead me to ascribe a polyphyletic origin to the freshwater 
sponges: these are their differences of form, their local dis- 
tribution, and further also the conditions of derivation which 
must necessarily be assumed for other freshwater animals, 
notwithstanding their great similarity. 
An artificial system will divide the freshwater sponges 
first of all into two great groups—those without and those 
with gemmules. In our consideration we shall also for the 
present accept these groups, although, as I will at once point 
out expressly, they cannot at all be regarded as natural and 
as expressing the true aftinities. 
The first group breaks up into the Lubomirskie and the Pota- 
molepides, to the latter of which belong the new species here- 
after to be described and probably also the genus Uruguaya, 
Carter. As regards the Lubomirskie, these may be the youngest 
of freshwater sponges which stillcome remarkably near to certain 
marine sponges ; close to them, and especially to L. papyracea, 
Dybowskyi, comes my Potamolepis Leubnitzie ; but probably 
uo one will venture to assert that these sponges are directly 
