SPONGES. 165 



parasites on other existences as wonderful as them- 

 selves, or float on the surface and in the depths in the 

 midst of a vegetation relatively rare."* 



5. Sponges. 



For a long time the zoophytes were taken for in- 

 durated marine plants. Their animal nature, and 

 their likeness to animals under forms and aspects so 

 grotesquely various, were not thoroughly recognised 

 until our own times ; the name they still retain re- 

 calls their apparent analogy to vegetables. 



Tlie characters of animality which they present 

 endure but for an insignificant period of their exist- 

 ence. At first they move freely in the water, some 

 solid body arrests them in their course, the young 

 animal whose body is sometimes — in the sponges, for 

 example — surrounded with vibratile ciliae, attaches 

 itself to the obstruction, where it soon loses all power 

 of movement, and commences a series of strange meta- 

 morphoses. The body, at first gelatinous, breaks 

 into holes, which change by extension into winding 

 canals, traversing the mass in all directions. In 

 these winding channels the water circulates, and 

 Urnigs to the animal whatever substance may be 



* Schleulen, La Plante el sa Vie. 



