ON THE FRESH-WATER SPONGE. 
143 
lays four eggs, greenish-yellow, spotted with brown, most thickly at the large 
end. The sexes are similar as regards plumage, but the female is somewhat 
larger than the male. 
August 9, 1839. 
CONTRIBUTIONS TOWARDS A MORE ACCURATE KNOWLEDGE 
OF THE FRESH-WATER SPONGE (Spongilla lacvstris). . 
By Professor Meyen, M.D. 
{Translated from, Mullers Archie fur Anatomic,Physiologie, u. Wissenschaftliche Medicin.) 
The Sponges of the fresh water have long been a source of trouble to the 
naturalist, since he knew not whether they should be placed amongst animals or 
vegetables. At the present time,however, I believe it may be assumed that they 
all belong to the animal kingdom. On a former occasion I proved that Spongia 
friabilis of Lamarck and Esper is nothing more than the skeleton of Alcyonella 
stagnorum (see Isis , 1828, p. 12.) ; at present I have various observations to 
communicate, showing that Spongia lacustris is also the residence of a Polyp, 
which in the mean time was rendered probable in the highest degree. Yet it must 
still be remarked, that amongst the forms known by the name of Spongia 
lacustris , certainly many at least specifically varying kinds are confused, a more 
accurate distinction of which will presently be given. 
Towards the end of last Summer I fished up from a considerable depth of 
standing water a number of the Spongia lacustris , the green and gelatinous sub¬ 
stance of which was already for the most part destroyed, so that the silicious ske¬ 
leton, consisting of the well-known Spongilla needles, was very easily observed. In 
the individual meshes which the needles of this skeleton form in their combination, 
lay the round whitish-yellow little bodies which are considered as the sporangia 
of these Sponges. They were of the size of the smallest Poppy-seed, and came 
gradually out of the meshes of the silicious skeleton after the entire had laid 
quiet for some months in my chamber. The more accurate consideration of these 
round bodies shows that they are formed in a manner entirely different from the 
sporangia of Algos , whilst they agree entirely with the so-called Winter gemmules 
( Winter-Eiern ) of Polyps. They are formed out of a firm and leathery mem¬ 
brane, which, except on a small round spot, is laid over their entire surface with 
a thick crust, and consists of very prettily-formed silicious bodies and carbonate 
of lime, which is situated with a cellular appearance between the regularly-placed 
silicious bodies. These bodies have some resemblance to those which appear on 
Polypiferous gemmules. They are about three-fiftieths of a millimeter in length. 
