SPONGES. 
4 5 
scribed, by -which a constant stream enters at the pores, 
and passes out at the oscula. The one is a mechanical, 
the other a vital operation. The latter is performed only 
during life and health, and contributes to the nourishment 
of the animal ; the former goes on after death, and is of 
no benefit to the Sponge, though very useful to its possessor. 
The one may be compared to that indiscriminate devouring 
of books, which wo sometimes see in great readers — a 
voracity insatiable indeed, but which leaves the mind as 
empty as it was before ; the other to that guarded selec- 
tive reading which ever watches to extract mental food, 
separating and rejecting by a secret, but potent alchemy, 
the useless and the bad. Or we may compare the one to 
a soul dead in trespasses and sins, incapable (because 
destitute of spiritual perceptions) of distinguishing truth 
from error, and thereforo carried about by every wind of 
doctrine of those who lie in wait to deceive, — the tools of 
Satan and his agents, whose purposes they are unconsci- 
ously serving. The other may be likened to a living soul, 
who brings everything to the touchstone of the Word, 
proving all things, and holding fast only that which is 
good, by which he is nourished and edified, his spiritual 
bfe is developed, and he grows in knowledge, in service, 
a nd in grace. 
Perhaps we may carry this parallel further. The eclectic 
process in the Sponges is not so simple a thing as might 
be supposed. From the common water, which bathes all 
alike, various and dissimilar substances aro separated, 
selected, and appropriated by different species. “For 
example, it is very common to find growing on the same 
1 °civ, or seaweed, a siliceous, a calcareous, and a horny 
