M. C. Mereschkowsky on a new Genus of Sponge. 75 
opinion of M. Hiickel that in order to be a sponge an organism 
must have not only spicules but also pores. 
With respect to the spicules of Wagnerella, we have seen 
(and I hope it is unnecessary to dwell upon this fact) that these 
spicules cannot by any means be regarded as foreign to the 
organism and borrowed from some other sponge (besides, 
the White Sea has no sponges furnished with spicules re- 
sembling those of Wagnerella), but that, on the contrary, 
we are led to the opinion that these spicules are produced by 
the sponge itself. 
It is therefore evident that Wagnerella belongs to the 
Calcareous Sponges, and notably to the family Ascones. As 
regards the genus, I find that the system of M. Hiackel, which 
is founded exclusively upon the spicules, is sometimes too 
artificial, and will become still more so in course of time. This 
system is founded principally upon the fact that the form of 
the sponge is a character too variable and inconstant to enable 
a system to be based upon it. Although in general terms this 
may be true, we nevertheless know, among the sponges, plenty 
of exceptions in which the form acquires so great a constancy 
that it may be employed not merely to characterize a species, 
but may even lead to the formation of distinct genera, as, for 
example, in the case of Cladorhiza. It is the same with our 
Wagnerella, of which the extreme smallness, the globular 
head supported by a long peduncle dilated into a cone at its 
base, are all constant characters, and consequently sufficient 
to bear one out in establishing a distinct genus. The few 
species of the genus Ascyssa, to which the animal might 
otherwise belong, are so little like Wagnerella that one 
would not hesitate in ordinary circumstances to form a sepa- 
rate genus for this organism. 
M. Hiickel, who has founded his genera upon different com- 
binations of three kinds of spicules, has by this means re- 
stricted for ever the number of genera; for all the possible 
combinations have been employed by him ; but it may be 
foreseen that Calcispongiz will probably be found so different 
from the known forms, that it will be perfectly artificial to 
range them in one of M. Hickel’s genera, and that, conse- 
quently, sooner or later it will be necessary to break through 
the boundaries laid down by him, and to found genera not 
only upon the combinations of the spicules, but also on their 
forms, the form of the body, and other characters. 
I propose to name this genus, which has the habit of Tis7- 
phonia agariciformis, and is furnished only with simple 
spicules, Wagnerella. ‘The diagnosis of the genus and that 
of the species will be as follows :— 
