ALLIES OF THE EARTHWORM 



233 



the body into the chitinous sheath (Fig. 115, 2), and other 

 muscles to extend the body again. Plumatella reproduces 

 by eggs and spermatozoa, by budding, and by statoblasts 

 (Fig. 115, 5). Statoblasts are internal buds developed from 

 cells lying upon the retractor muscle, and are covered with a 

 chitinous shell. In case the colony freezes in winter, or the 

 pond dries up, the statoblasts remain alive, and on the return 

 of favorable conditions start a new generation. 



The class of which Plumatella is an example is called 

 sometimes Polyzo'a, and sometimes Bryozo'a. Most of the 

 members of the class live in the sea as mat-like or moss-like 

 fixed colonies. On account of their brownish color and deli- 

 cate texture some of these colonies are fre- 

 quently mistaken for brown seaweeds. 



The Brachiopod. The first impression that 

 the casual observer has of the animal repre- 

 sented in Fig. 116 (Lin'gula lepid'ula) is that 

 he is looking at some kind of a clam, 

 an impression given by the two calcareous 

 valves which inclose the body proper ; but 

 the brachiopod is not a clam. It lives at the 

 bottom of bays, and is found most abundantly 

 in the waters of Japan. It has a shell from 

 one half inch to one inch in length, and a 

 stalk called the peduncle, two or three times FIG. 116. Brachi- 

 as long. Professor E. S. Morse, of Salem, P d - Natural 

 Massachusetts, has witnessed the activities 

 of various species of these animals, and has 

 written interestingly 6f their habits. When undisturbed in 

 a sea-water aquarium, Crlottid'ia pyramida'ta (Fig. 117) lies 

 with part of its body above the sand. The valves open 

 slightly, and the bristles, extending from between the valves, 

 are grouped roughly into three tubes. The lophophore makes 

 a waving motion which sets up currents in the water, as 



size. (After 

 Morse) 



