WORMS. 



67 



-with its eyes and the long proboscis-like appendage, while at about the 

 middle part of the body these are repeated. These latter belong to the 

 new worm, which is about to separate from its parent. 



Fig. 63. — Fresb-water worm (Xais) reproducing by fission. 



The worms with many bristles (Polychseta) are almost exclusively 

 marine ; indeed, the only exception that suggests itself at the moment of 

 writing is a form found in the Schuylkill River, near Philadelphia, to 

 which the barbarous name Manayunlda has been applied. The Polycha^ta 

 are divided into two divisions, in which details of structure agree more or 

 less closely with habit. The first group — that which follows out the 

 main vermian line — embraces forms which wander freely through the 

 water, or the mud and sand ; the members of the second group are seden- 

 tary in habit; miost of them build tubes, — sometimes of sand or gravel 

 cemented together, sometimes of carbonate of lime, — and in these their 

 life is spent,. 



Of the errant forms, the most familiar are the 'clam-worms,' the 

 nereids of science. Of these there are many species, which sometimes 

 burrow through the mud, while frequently they may be taken swimming 

 at the surface of the water. They are well known to the clam-digger. — 

 he throws them up by the hundreds as he digs for his clams. — but you 



