LIEBERKiiHN, ON SPONGILL.E. 
217 
Lieberkuhn notices four kinds of gemmules characterised 
respectively by their cases or shells : 
1. Those with smooth cases. 
2. Those with stellate amphidiscs. 
3. Those with amphidiscs^ in which the discoid extre- 
mities are entire and not stellate. 
4. Gemmules^ whose case^ instead of amphidiscs, is 
furnished with minute, usually slightly curved, siliceous 
spicules. 
Motile spores. 
[Besides the gemmules above described, other reproductive 
bodies are met with in Spongilla : 1 . Some, which from their 
resemblance to the motile spores or zoospores of many plants, 
have also been termed '^'^schwarm-sporen," or "motile spores;" 
and 2 others, which, from their resemblance to the spermatic 
filaments elsewhere met with, are, as it would appear, pro- 
perly denominated zoosperms," or " spermatozoids."] 
These bodies are thus described by the author, who states 
that he first discovered the "motile spores" after having left 
some recently collected Spongilla for a few hours in a vessel 
filled with river water. They are recognisable by the naked 
eye, having a longitudinal diameter of pretty nearly two 
thirds of a millimeter, and of one fourth in the greatest 
transverse diameter. They vary, however, considerably in 
size, and are of an ovoid form. In most of them, without 
the aid of glasses, a transparent hemispherical space may be 
perceived in the anterior, and a brilliant white space in the 
hinder part of the body. These terms are applied, because in 
swimming the weakly refractive part precedes, and the other 
follows. The spores move actively about in all directions. After 
existing about two days in this motile condition, the spores 
become quiescent and subside to the bottom, where most of 
them perish altogether. They rarely become developed. 
On the twentieth day, in a successful observation, the 
author noticed that the spot formed by the subsided spore 
was increased in size, and upon examining this, it was found 
to exhibit the constituents of the young Spongilla, that is to 
say, protean cells, smaller and larger spicules, and a few germ- 
granules. 
The movements of the spores were efifected by means of 
cilia, uniformly distributed over the surface, and in length 
about the same as those of the Turbellaria, though perhaps 
still finer. But what distinguishes them essentially from the 
