BRANCH PORIFERA: THE SPONGES 



others in deeper water, even to the deepest depths yet 

 explored. They are found in all seas, though especially 

 abundantly in the Atlantic Ocean and Mediterranean Sea. 

 Form and size. The shape of the simplest sponges is 

 that of a tiny vase or nearly cylindrical cup, hollow and 

 attached at its base. At the free end there is a large 

 opening. But there is a great deal of variety in the form 

 and size of different sponges. 

 There is, indeed, much varia- 

 tion in the shape and general 

 character of different individuals 

 of the same species. Unlike 

 most other animals, sponges are 

 fixed, and the character of the 

 surface to which a sponge is 

 attached has much influence 

 upon its shape. If this surface 

 is rough and uneven the sponge 

 may follow in its growth the 

 sinuosities of the surface and so 

 become uneven and distorted 

 in shape. At best, only a few 

 kinds of sponges have any very 

 even and symmetrical shape. 

 Most of them are very unsym- 

 metrical and grow more like a 

 low compact bushy plant than 

 like the animals we are familiar 

 with. The smallest sponges 

 are only I mm. (^ in.) high, 

 while the largest may be over FlG - I2 - The skeleton of a 



... "glass " sponge (skeleton com- 



a meter (39 in.) in height. In posed of siliceous spicules) from 

 color living sponges may be J ;l P :xn - < From specimen, j 

 red, purple, orange, gray, and sometimes blue. Most 

 sponges have the whole body of one color. 



