THE NATTTKE OF SPONGES. 
169 
Every portion of the sponge, in a live state, is covered with fleshy 
material sarcode , much like that of infusorial animals. De- 
tached portions of this sarcode have been described by Carter 
as moving somewhat like amsebse, and Bowerbank observes : 
“ I have frequently, at different seasons of the year, taken por- 
tions of the sarcode from living and healthy specimens of spon- 
gillae in which I could not, by the closest attention, detect 
these motions, which are so readily seen at other periods of 
•their existence : and even at the same period of the year, the 
sarcode of some specimens exhibits these motions, while in 
others they could not be detected.” This passage suggests in- 
teresting experiments, which our readers may easily make when 
spongillse occur amongst their captures on collecting days. 
According to Bowerbank, a power of 500 or 600 linear enables 
the microscope to show that in a living sponge the whole of the 
sarcode abounds in nutrient particles, “ some simply adhering 
to the surface, while others are imbedded at different degrees 
of depth.” It should be added, that this sarcode sub- 
stance is sensitive to external impulses, and contracts under 
conditions that would create alarm in creatures of higher or- 
ganisation capable of a mental impression. It has muscular 
power, nervous power, and digestive power, without any dis- 
tinction of organs being visible. 
The roots of sponges are simply means of adhesion, or 
anchoring, whether they present the simple form of a sort of 
cement attaching them to rocks, or of glassy fibres, like the 
Glass Rope Sponge, penetrating into mud. In no case have 
they anything to do with nutrition. 
Sponges are not exactly like plants, dependent entirely upon 
what air or water may bring to them for nutriment. They 
possess a ciliary apparatus, by which they can make artificial 
currents subservient to the purposes of food collecting, aeration, 
&c. Sponge gemmules also, by means of cilia, can travel about 
until they find an appropriate resting-place, and commence a 
sedentary life. The propagation of sponges takes place by eggs 
(ova), by buds (gemmules), and by divisions, such as is common 
with the infusoria. 
The preceding statements may excite curiosity to know more 
of these organisms, and prompt many readers to consult various 
writings on the subject. For the present object of introducing 
Professor H. James Clark’s researches, we have perhaps said 
enough concerning the general characters of sponges, and shall 
now pass to a brief consideration of polyps, to which Haeckel 
and others assimilate them, and which notion Mr. Clark disputes, 
as many English observers have done and still do. 
All microscopists know the common freshwater polyps. They 
belong to the sub-kingdom Coelenterata, and to its lowest type. 
