SOME MOOT POIXTS AV NATURAL HISTORY. 251 



mats, as cast up on our coasts, present us with perfect 

 imitations of pieces of pale-brown sea-weed (Fig. 37) ; and 

 in this mistaken light they are duly gathered, and frequently 

 figure as undetermined species of marine plants in the 

 herbaria of collectors. The microscopic investigation of a 

 sea-mat, or even the close inspection of the larger species 

 by the unassisted sight, at once reveals the fact that the 

 supposed sea-weed represents in reality the remains of a 

 colony of animals. The dried organism is made up of 

 hundreds of little oval cells (b), packed as thickly as they 

 can lie on each side of the structure. Could we observe 



a 



FIG. 37. a, Flustra, or sea-mat, natural size ; b, a small portion magnified, showing 

 the cells. 



the colony in life, we should find each cell to be occupied 

 by a little animal, provided with a beautiful crown of delicate 

 tentacles, which are continually being protruded from and 

 withdrawn into the little abode ; thus accomplishing the im- 

 portant actions of obtaining not only food, but also oxygen 

 for breathing from the water around. Once again, we thus 

 meet with a colony of animals growing rooted and fixed like 

 a true plant, and enlarging its existence by a process of 

 budding, strictly comparable with the similar process on 

 which the increase of plants depends. 



Little need be said in addition to these examples to 



