B. V.] THE HISTORY OF ANIMALS. 119 



the case with all other fixed things, that they derive their 

 food from the spot to which they are attached. 



3. The compact species are weaker than those which are 

 thin, because their point of attachment is smaller. It is 

 affirmed that the sponge possesses sensation; this is 

 a proof of it, that it contracts if it perceives any pur- 

 pose of tearing it up, and renders the task more difficult. 

 The sponge does the same thing when the winds and waves 

 are violent, that it may not lose its point of attachment. 

 There are some persons who dispute this, as the natives of 

 Torona. The sponge is inhabited by worms and other living 

 creatures, which the rock-fish eat when the sponge is torn 

 up, as well as the remainder of its roots. But if the sponge 

 is broken off, it grows again, and is completed from the por- 

 tion that is left. 



4. The thin sponges are the largest, and they are most 

 abundant on the Lycian coast ; the compact sponges 

 are softer, and the Achillean are more harsh than the 

 others. On the whole, those that inhabit deep places with 

 a mild temperature are the softest, for wind and cold 

 weather harden them, as they do other growing things, and 

 stop their increase. For this reason the sponges of the 

 Hellespont are tough and compact ; and, altogether, those 

 beyond Malea, and those on this side, differ in softness and 

 hardness. 



5. Neither should the heat be very great, for the sponge be- 

 comes rotten, like plants, wherefore those near the shore are 

 the best, especially if the water is deep near the land, for the 

 temperature is moderated by the depth. "When alive, before 

 they are washed, they are black. Their point of attach- 

 ment is neither single nor dispersed over the whole surface, 

 for there are empty passages between the points of attach- 

 ment. Something like a membrane is extended over their 

 lower part, and the attachment is by several points ; on the 

 upper part are other closed passages, and four or five which 

 are apparent. Wherefore some persons say that these are 

 the organs by which they take their food. 



6. There is also another species called aplysia, because it 

 cannot be washed. This has very large passages ; but the 

 other parts of the substance are quite compact. When cut 

 open it is more compact and smooth than the sponge, and 



