238 Miscellaneous. 
nature are described by Lieberkiihn in his recent memoir on the 
Spongille. 
The parenchyma of the body of the Spongille presents a very 
variable arrangement, whilst the siliceous skeleton retains the same 
characteristic form in all specimens. Sometimes the parenchyma 
exhibits a cavernous structure, containing cavities more or less iso- 
lated from each other, and connected either with the orifices of 
ingestion or with tubes of ejection; sometimes these cavities are 
replaced by a system of canals extending through a great portion of 
the Sponge, and opening directly into the tube of ejection; in this 
case a great part of the integument is destitute of orifices of in- 
gestion. In other cases the cutaneous pores are dispersed in great 
numbers over the whole surface of the Sponge, and usually lead into 
a large cavity belonging to the system of ingestion. The walls of 
the partitions bounding these cavities bear vibratile apparatus. In 
other Spongille there do not exist membranous partitions bounding 
the cavities ; but the body is traversed in all directions by trabeculee 
of different thicknesses, which are often supported upon the integu- 
ment. Some of these are completely smooth in appearance, and 
show no appreciable outlines of cells; the strongest bear vibratile 
apparatus: others are constricted like a necklace, being formed of a 
simple series of cells in juxtaposition. Others, again, are composed 
of several rows of cells, of which the limits are visible only at the 
surface (so as to resemble an epithelial coat) or only at the centre of 
the trabecula. 
All these different appearances may be presented successively by 
one and the same Spongilla. Homogeneous parenchymatous parti- 
tions have contracted, under the eyes of M. Lieberkiihn, into trabe- 
culee with a cellular structure and of a necklace-like form. On the 
other hand, he has seen neighbouring trabeculz spread out and be- 
come united in such a manner as to form a membranous wall. The 
cavities open into one another, and separate again. Fragments of 
Spongille artificially detached prove that the cells of the parenchyma 
can unite in a few hours to form a cutaneous envelope. 
The pores of ingestion are not characteristic of the integument, as 
perfectly similar orifices are seen to originate in the membranous 
partitions of the interior of the body. The tubes of ejection are the 
seat of very peculiar movements. The author has seen the cells of the 
innermost layer gliding up the wall of the tube, and again descending. 
M. Lieberkiihn has positively demonstrated a fact which has only 
been suspected since the observations of Laurent—namely, the re- 
production of Sponges by spontaneous division. In individuals kept 
in vessels filled with spring water he has seen the body contract, 
and emit here and there processes, which soon became detached and 
glided over the vacant portions of the siliceous skeleton, and even 
upon the bottom of the vessel. This division appears only to take 
place in individuals which are nearly perishing. But the fragments 
thus set free continue to live, and in the course of a few weeks they 
have produced in their interior siliceous spicules and vibratile cilia. 
In these fragments of Spongille, and in perfect individuals in a 
dying state, M. Lieberkiihn has witnessed phenomena which might 
