Chap. 27 AN AQUATIC MISCELLANY 547 



Fresh-water bryozoans do not produce free-swimming larvae but bear in- 

 ternal buds or statoblasts that develop directly into colonies like the gemmules 

 of sponges (Figs. 22.7, 27.13). Most bryozoans exist only as statoblasts during 

 the winter. Many of these are banded with air cushions that buoy them up, 

 and armed with circlets of hooks that catch on the feathers and feet of ducks. 

 Statoblasts are carried far and wide by birds and currents of water. Occa- 

 sionally, they are washed out along the shores of lakes and lie in countless 

 numbers, long dark ribbons of them on the beaches. 



Phylum Brachiopoda — Lamp Shells 



Their Great Past. These animals were named brachiopods because some- 

 body mistook their long lips for arms, and lamp shells because their shells 

 suggested miniature Roman oil lamps. 



Brachiopods have had a great past in numbers, diversity, wide distribution, 



Air cells 



Germinating 

 area 



B. GERMINATING 

 STATOBLAST 



A. RESTING STATOBLAST, 

 OR INTERNAL BUD 



Esophagus 



"- " I Tl III ilT 



SECTION OF MATURE COLONY 



Fig. 27.13. Fresh-water bryozoan, Pliimatella repens. Animals drawn greatly 

 enlarged with their tentacles expanded, or withdrawn; both contain developing 

 statoblasts. A, statoblast, about the size of a fig seed, with horny covering and 

 band of air cells. B, in the germinating statoblast the young animal has split the 

 shell revealing its body and yolky food. (After Brown, Trans. Amer. Micr. Soc. 

 53:427, 1934.) 



