82 SPONGES 
not be washed clean. He appears to be undecided in opin- 
ion whether to consider them plants or animals, or probab- 
ly it would be most correct to say that he considers them 
neither, but as a kind of intermediate between the two. 
Pliny who, although he copies most of his account of 
sponges from Aristotle, is never afraid to give an opinion 
of his own, seems to consider them as animals. At first he 
declares they have a third or middle nature, and are neither 
living nor yet plants. This statement is evidently derived 
from Aristotle, but later comes his own idea, for he declares 
most emphatically that sponges not only have life, but a 
“sensible life” for it is found that they have blood settled 
within them. He also decides that they have the sense 
of hearing which causes them to draw in their bodies at 
any sound, thereby squeezing out water contained within 
their tissues. He says that they cling so hard to the rocks 
that they have to be cut away, and that they then shed 
blood plentifully, or that which resembles blood quite close- 
ly. Pliny further gives us the idea that there are two sexes 
