with some Remarks on the Nature of the Spongiæ Marine. 383 
These gemmules with their numerous cilia may be seen, on referring to the 
drawings that accompany Dr. Farre's paper, in Phil. Trans., plate 26, at figs. 
20—23, where they are delineated on an enlarged scale. 
Dr. Grant has likewise published some observations on the spontaneous 
motions of the ova of several Zoophytes, well worth perusal, in the Edinb. 
New Phil. Journ. for 1826, at p. 150 and the following pages“. 
Now, by comparing these descriptions with those before given of the germs 
or sporules of Ectosperma, and of the germlike bodies both of the Spongilla 
and of the Spongiæ, it will be evident that these gemmules possess far more 
vigorous and rapid powers of locomotion, arising doubtless from their finlike 
cilia, and their actions exhibit more volition or a greater degree of spontaneity, 
and precisely that which usually pertains to animal life : wherefore, they more 
nearly resemble in those powers the Infusorian Volvox. It likewise appears 
from those authors, as well as from the earlier accounts of Cavolini, that the 
gemmules of Zoophytes frequently change their forms in swimming, that 
they have considerable powers of contraction and dilatation of their whole 
bodies, and are otherwise highly irritable; hence, in these characters they 
present an essential difference both from the sporules of the River Sponge, and 
from the germlike bodies of the Sea Sponges}: but these gemmules, in respect 
to their irritability alone, much nearer approach the Infusoria; and thereby, 
I think, their animal nature is sufficiently established. Also we know from 
Dr. Unger's very conclusive experiments, that the locomotive sporules of the 
Ectosperma are those of a true plant; and since the moving germlike bodies 
of both kinds of Sponge are much more analogous in every respect to those, 
* And for that author's account of the ova of Flustre, see the same Journal for 1827, p.116. I 
must however object to the term ova (eggs) being used to designate the reproductive bodies (gem- 
mules) of Zoophytes: because, these being enveloped by a mere skin or membrane, usually furnished 
with cilia, endowed with irritability or powers of contraction and dilatation, and frequently, if not al- 
ways, possessed of some kind of muscular apparatus, are rendered totally distinct from any ova or 
ovula, i. e. such reproductive bodies as are simply inclosed within unorganized coverings or plain ex- 
ternal shells, Although Dr. Allan Thomson incorrectly considers the distinction between eggs and 
gemmules to be somewhat arbitrary. Vide note at p. 46 of Johnston's Brit. Zooph. 
T Dr. Grant positively asserts the ova of the Sea Sponges “ do not change their forms while 
swimming, (p. 154, loc. cit.) And I have not witnessed either any such changes, or any symptoms 
of irritability, in the sporules of the River Sponge. 
VOL. XVIII. 3E 
