Vol. IX, No. 1.] Sponges of the Lake of Ttberias.. 83 
[V.8.] 
experiment to lose its power of producing gemmules in peculiar 
circumstances, the fact would not provide a valid argument 
against the retention of a separate genus of which the chief 
generic character was the invariable absence or degenerac 
of the gemmules. In any case, it seems to me more satisfac- 
tory to call species of a certain facies in which no microscleres 
have been found, by some such name as Nudospongilla, rather 
than to refer to them vaguely as ‘‘ Spongilla (*) sp.’’; for it 
has been recognized that the specific characters of many such 
species are well marked, and specific names have been conferred 
on fend although their genus has been queried. 
ortispongilla stands on a somewhat different footing, for 
it possesses positive structural characters that separate it from 
all other freshwater sponges. It is perhaps actually related to 
wae eset its resemblance to Veluspa (Lubomirskia) being 
apparently superficial and due to convergence rather than 
genetic a nship. 
ecognition of the subfamily Potamolepidinae as here 
dagnade Renna to some extent on the fact that no gemmules 
have been found in any species that can be definitely assigned 
to the genus Potamolepis. This genus is known from but a 
few specimens, although it is apparently far from uncommon 
in certain parts of the Congo basin. None of these few speci- 
gotten that many encrusting Spongillidae (notably some species 
f Corvospongilla) produce gemmules that adhere firmly to 
Specimen is removed for preservation. There is, therefore, a 
considerable chance of their being overlooked when it is exam- 
ined in a museum. We know that some Nudospongillae do 
produce gemniules, but that these gemmules, which are not 
always present, are less highly organized than those of the 
Spongillinae and entirely lack microscleres. Possibly those of 
Potamolepis are of a similar nature, if they are ever produced : 
those of Veluspa are not very dissimilar. If so, no difficulty 
pewnandtrantiog I am inclined to think that this stadt may 
ultimately prove necessary. Perhaps, however, the genera 
ictyum and Cortispongilla will be f found, a the minute 
anatomy of the Moxaxonida is better known, to be widely 
different in organization from all eae bedsiwites genera and 
