WORMS 173 



parapodium is a bunch of bristles, or chcette. There are hundreds 

 of species of this class of worms, the species being based on the 

 shape and the lobes of the parapodia, the relative length of the cirri, 

 the form and arrangement of the chaetee, and so on. They are 

 abundant on the shore everywhere, but abound where rocks and 

 stones afford them some shelter. Many burrow in the sand and 

 mud. In doing this the worm eats his way into the hole, swal- 

 lowing the mud and sand. He assimilates the organic or vege- 

 table matter the mud contains, and ejects the rest in cylindrical 

 coils, known as castings, which lie in heaps at the mouth of the bur- 

 row. By these castings they may be traced. Others secrete tubes. 



The polychaete worms are divided into Errantia, which are 

 wandering, free-swimming forms, and Sedentaria or Tiibicola, 

 which live in tubes permanently. These distinctions are not 

 strictly correct, since some species of errant polychaetes form 

 tubes (Bunicidce), and some Sedentaria form no tubes. 



Many polychaetes are beautifully colored, some in vivid reds 

 and greens, with various markings; some are iridescent; some 

 are phosphorescent. 



ORDER ERRANTIA 



Carnivorous, free Polychceta, with protrusible pharynx armed 

 with a horny jaw. " They are active, fierce beasts of prey." 



FAMILY SYLLIDJE 



This family is the highest in organization of the worms. They 

 are small, the majority being less than an inch in length, and 

 many are minute. They are often highly colored. Many have 

 long cirri on the feet; some have alternation of generation. 

 They are common everywhere along the coast, but are not seen 

 unless searched for. Sponges sometimes are alive with them. 

 They are interesting subjects for microscopic study. 



FAMILY APHRODITIDJE 



The scale-bearing annelids. This family of worms is distin- 

 guished from all others by having scales on the back. The scales, 

 called elytra, are flattened dorsal cirri carried on the upper para- 



