AND PHYSIOLOGY OF THE SPONGIAD^. 
819 
and 43, Plate XXVI. Phil. Trans. 1858, represent the spicula of the larger description 
of gemmule of Tetliea cranium^ after separation by nitric acid. 
The reproductive bodies in the Tetliea described by Professor Huxley do not resemble 
those in T. cranium ; no spicula are either described or figured as existing in them, and 
in this respect they appear much more to resemble the reproductive organs described 
by Dr. Graxt as existing in the Halichondraceous sponges of the Firth of Forth. But I 
am not surprised at this discrepancy, as in Tethea simillima, Bowerbank, MS., in the col- 
lection of the Koyal College of Surgeons, from the Antarctic regions of the South Sea, a 
species very closely resembling T. cranium, the gemmules are so like those of the latter 
species as not to be readily distinguished from them in their natural condition ; but vrhen 
microscopically examined, not the slightest trace could be found of the smaller, and 
what I conceived to be the male gemmule in T. cranium. I have several other species 
of Tethea in my possession, but I have not yet found gemmules in the interior of any 
of them. 
External Gemmulation. 
In Tethea Lyncurium we have gemmules produced externally, which are perhaps much 
more entitled to that designation than any of the reproductive organs previously 
described. The fasciculi near the base of the Tethea are protruded considerably beyond 
the surface of the animal, and at the termination of each there appears a small mass of 
sarcode, which assumes a more or less globular form. If their bodies be immersed in 
Canada balsam and examined microscopically, they will be found to contain not only the 
spicula projected from the parent, but a second series, which have been secreted in the 
mass, and which have assumed the mode of disposition so characteristic of the skeleton of 
the parent Tethea. I am indebted to my friend Mr. T. H. Stewart for this interesting 
fact, and for the specimens illustrating it. They were found in Plymouth Sound. 
Fig. 19, Plate XXXIV. represents one of these gemmules with a portion of the 
skeleton fasciculus on which it is produced, under a linear power of 50. 
Propagation by Sarcodous Pivision. 
The fact of the resolution of the sarcode of the interstitial tissues of Spongilla into 
small masses of unequal size and variable form has long been known to naturalists, and 
that when separated from the parent body each becomes capable of locomotion, and of 
ultimately becoming developed into a perfect sponge. Carter, in his valuable paper 
published in the Journal of the Bombay branch of the Royal Asiatic Society, No. 12, 
1849, has given a minute account of their structure and motions when separated from 
the species which form the subjects of his paper, and his descriptions are in perfect 
accordance with the similar bodies separated from our European species S.Jluviatilis, 
which I have had frequent opportunities of observing, and of confirming the history 
given by him of their locomotive powers and continual inherent motions. The author 
designates these bodies “ sponge-cells,” and treats of them as if they had a well-defined 
cell-wall, while their eccentric changes of form are perfectly inconsistent with such a 
MDCCCLXII. 5 T 
