98 Dr. F. Vejdovsky’s Contributions to the 
mentioned species, or as a distinct species, I cannot at present 
decide with certainty. 
II. Trochospongilla erinaceus was found in cushion-like 
stocks in a deep side-water of the Elbe, near Neratovic. The 
inferior layers of the lamelle contain extraordinarily nume- 
rous gemmules, seated close together, as shown in fig. 8. The 
longitudinal section through a gemmule (fig. 5) presents the 
following interesting characters :— 
1. The inner chitinous membrane is very thick and layered 
(fig. 5, c). 
2. The very depressed amphidisci (+) are in direct con- 
nexion with the chitinous membrane. 
3. The layer representing the parenchymatous envelope of 
the other Spongillidzs is peculiarly modified in T'rochospon- 
gilla. When the surface of the gemmule is examined it 
appears to be composed of five- or six-sided prismatic spaces 
(fig. 4). Longitudinal sections, however, show that this 
layer consists of tall hollow columns (fig. 6), which are divided 
by transverse walls into a number of air-chambers. The 
walls are firm, not very flexible, shining, and probably com- 
posed of a chitinous substance. ‘The interior space becomes 
filled with air. 
The whole of this outer envelope evidently forms an aero- 
static apparatus as a means of the more ready transportation 
of the gemmule, and perfectly corresponds to the natatory 
rings of the statoblasts of the freshwater Bryozoa. 
Whether the North-American species with smooth-edged 
amphidisci, Meyenia Leidii and MM. gregaria, possess corre- 
sponding envelopes, must be ascertained from fresh material. 
I cannot detect the air-chamber layer in the dry Meyenia 
Leidii transmitted to me for comparison by the kindness of 
Mr. H. J. Carter. 
Ul. Ephydatia fluviatilis, aut., I have also obtained from 
the neighbourhood of Sobeic (Ostromér), out of stagnant 
water, and found that it agrees perfectly in its characters with 
the sponges of the same species that I have described in my 
monograph. 
By the kindness of Mr. H. J. Carter also, [have been enabled 
to compare the English specimens of this species with our 
indigenous ones, and from this comparison it appears that the 
English “ Meyenia fluviatilis, Carter,” is identical with my 
Ephydatia fluviatilis. 
EXPLANATION OF PLATE VI. 
Fig. 1. Ephydatia amphizona, n. sp.; gemmule very slightly magnified. 
Fig. 2. The same species. A nearly median longitudinal section (magn. 
