Dr. W. Marshall on new Siliceous Sponges. 397 
main uncovered through the winter, have harder shells than 
those of Bomb. dispar, which are clothed with a_ hairy 
covering.” 
There is nothing with which the gemmules of the Spongille 
can be better compared than with the statoblasts of the fresh- 
water Bryozoa; and this comparison holds good and has been 
earried out * in every particular. Both are acquired under 
the same circumstances ; both are portions of the main organ- 
ism separated for the purpose of asexual reproduction ; and 
they agree so closely, even in detail, in their structure, that 
Carter finds the only difference between them in their size 
and form. The statoblasts of the Bryozoa indeed have no 
armature of siliceous spicules, but yet their shells often possess 
peculiar contrivances which practically represent these in 
function. It is a fact of particular interest that, just as there 
are freshwater sponges without gemmules, there are also 
freshwater Bryozoa, not indeed without statoblasts, but with 
very slightly developed ones. The sponges in question are 
the Lubomirskiew, which undoubtedly are perennial, like the 
marine sponges; some of them, indeed, attain great dimen- 
sions (they occur as much as 60 centim. in height), and it is 
not very probable that such a growth, not bound to an incrust- 
able support, such as the twig of a plant, can take place in 
the course of a single summer. I know very well that Spon- 
illa-stocks of considerable size are occasionally referred to, 
but the statements relating to them are not remarkable for 
accuracy ; we are not informed whether these large specimens 
erew freely or whether they coated a branch, which, how- 
ever, makes a very important difference; whether they were 
in full life throughout, or whether these giants were not per- 
haps an accumulation of different years, of which only the 
outermost part was still living. Moreover perennial individuals 
which im consequence grow to a considerable size are by no 
means inconceivable in suitable localities, and in these the 
formation of gemmules might then cease, or indeed, under 
certain circumstances, need never be acquired, as is the case 
in the Lubomirskic, ‘These stand in the same relation to the 
other freshwater sponges as Mredericella sultana to the other 
Bryozoa of the fresh waters; the latter, according to W. 
Houghton {, is perennial, and certainly the small develop- 
ment of the statoblasts of this very species demonstrated by 
Allman is due to this circumstance. 
* F. J. F. Meyen in Miiller’s Archiv f. Anat. und Physiol, 1839, 
p. 83; H. J. Carter, “ On the Identity of the Seed-like Body of Spongilla 
with the Winter-egg of Bryozoa,’ in Ann, & Mag. Nat. Hist. ser, 3, 
yol. iii. p. 339 (1859). 
t+ Ann. & Mag. Nat. Hist. ser. 5, vol. vi. p. 389. 
