LIEBERKUHN, ON SPONGILLiE. 
213 
by Dujardin, or referable to a process of decomposition. 
Other portions presented on part of their surface a kind of 
long cilia, by means of which they moved rapidly from place 
to place, throwing out, at the same time, processes from the 
non-ciliated part of the surface, and again retracting them, 
exactly as do the Amcebce. Lieberkiihn never observed the 
ciliated particles in the winter, nor before the spring ; in the 
former season he noticed only those exhibiting the amseba- 
like motion. But these portions, which are always to be 
obtained when a living Spongilla is spread out upon the 
object-glass, are by no means amorphous masses, as figured 
by Dujardin, but among them may frequently be recognised 
structures having the form of a cell ; and this is the case 
more especially in the winter, at which time the granular 
substance is less abundant. When the amseba-like movement 
has ceased, these bodies are seen to contain a nucleus and 
nucleolus. The entire sponge is composed of this kind of 
substance. Though employing for convenience the term 
cell,^^ Lieberkiihn states that he has never succeeded in 
discerning a cell-membrane around these particles. 
Among these " cells " he often observed bodies containing 
foreign substances, such as Bacillaria, &c., but which, in 
other respects, fully resembled the sponge-cells, and were 
also furnished with a nucleus, though unprovided with a 
contractile vesicle. They protruded and retracted motile 
processes, and it is not impossible, he thinks, that they may 
really be Amcebce^ which are sometimes without a contractile 
vesicle. Actual AmcebcB with a contractile vesicle are by no 
means rarely contained in the sponge. 
The Spongill(B in general, especially in winter, are the 
habitation of an abundant infusorial life; he has observed 
abundance of Paramecium aurelia, P. colpoda, Chilodon cucul- 
lulus, TracheliuSj Amphileptus, Prorodon, Loxodes, &c. 
The gemmules. 
The living Spongillae are often seated, not immediately 
upon the wood, stone, &c., upon which they may be growing, 
but separated from it by a peculiar, dark-brown substance 
often several inches thick. This mass is composed chiefly of 
the remains of the dead sponge, empty gemmule-cases with 
their amphidiscs, various forms of siliceous spicules, &c. ; 
and occasionally there may be found in it gemmules still 
retaining their brown colour and contents capable of deve- 
lopment. 
Dead Spongillce are sometimes so thickly studded with 
gemmules as to present in consequence a gray or greenish 
