344 Dr Grant’s Observations on the Structure 
rous discoveries, both respecting the chemical principles and the 
actual existence of polypi, in many of the supposed marine 
plants, brought to light by Marsigli, Geoffroy, Lemery, Xmper- 
ati, Gesner, Peyssonell, Cavolini, Trembly and Ellis, the dis- 
tinct animal odour possessed by many sponges, both in their 
fresh and burnt state ; the abundant gelatinous matter which 
occupies the interstices of the horny fibres ; the palpitation of 
the fecal orifices, alleged by Marsigli, and the discharge of ex- 
crements from these apertures, discovered by Ellis, at length 
compelled naturalists to return to the ancient opinion of the ani- 
mal-nature of the sponge, and to regard it as a kind of ambigu- 
ous zoophyte or animal, approaching nearly to the form and na- 
ture of a plant ; in which opinion most zoologists at present 
agree* Linnaeus himself changed his former opinion of its vege- 
table nature ; and in the later editions of his Sy sterna Natures , 
classed it among animals. 
The contractile power formerly ascribed to it by the Greeks, 
was again revived rather from principle than from actual obser- 
vation ; and as this property had not been very distinctly mani- 
fested to modern zoologists, the statement of the ancients was 
adopted under a modified form. The sponge was now said to 
exhibit a kind of trembling motion when touched; and this 
equivocal sign of irritability is now ascribed to it by almost every 
modern zoologist. Cavolini and Montagu were of a contrary 
opinion ; they considered the sponge as destitute of irritability ; 
but from the want of decisive experiments, the most eminent na- 
turalists still continue to ascribe that property to it, believing it 
somehow essential to its existence as an animal. It has been 
very recently stated by Mr Gray, that the small hard spherical 
opaque grains, disseminatedin groups through the substanceof the 
Spongilla, a genus considered as nearly allied to the present, and 
which Linnaeus formerly considered as the grains or seeds of this 
fresh-water plant, actually enlarge, and become distinct spongillae, 
when preserved for a few days in water ; and from analogy 
with this substance, it is again maintained, that the true sponge 
is a marine plant, containing similar clusters of grains, and, con- 
sequently, a being destitute of contractile power. 
Pallas, Solander, Ellis, Gmelin, Bruguiere and Lamouroux, 
consider the contraction of the sponge when touched, as an ef- 
