88 ECONOMIC ZOOLOGY AND ENTOMOLOGY 



a circlet of vibrating cilia, which has suggested the common 

 name. These little animals are interesting on account of their 

 remarkable power to withstand drying. When the water in 

 which they are found evaporates, some of them do not die but, 

 as minute shrivelled dust-like particles, may lie for months 

 or even years and be revived again when water reaches them. 

 The Sea-mats and the Lamp -shells, Branch Molluscoida 

 (Mollusca, mollusc; Gr. eidos, likeness). The sea-mats, or 

 Polyzoa, are common on rocks along the seashore and sometimes 

 in fresh water also. Most of them either spread mat-like 

 over the surface of the objects on which they are growing, or 

 form branched tree-like or moss-like colonies and look much 

 more like plants than animals. Only their development 

 suggests any relation to the worms. The lamp-shells, or 

 Brachiopoda, are all marine. They look so much like little 

 clams that for a long time they were classed with the molluscs. 

 Their chief interest lies in the fact that they represent a group 

 of animals that were once very numerous but which have not 

 been able to adapt themselves to the changed conditions that 

 are found on the earth to-day. In ages past they seem to have 

 occurred in great numbers, as more than a thousand species 

 have been preserved as fossils in the rocks. To-day only 

 about one hundred species are known, and some of these are 

 very rare. 



