WORMS 173 
parapodium is a bunch of bristles, or chetw. 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 chete, 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 deing 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 polychete worms are divided into Errantia, which are 
wandering, free-swimming forms, and Sedentaria or Tubicola, 
which live in tubes permanently. These distinctions are not 
strictly correct, since some species of errant polychetes form 
tubes (Hunicide), and some Sedentaria form no tubes. 
Many polychetes are beautifully colored, some in vivid reds 
and greens, with various markings; some are iridescent; some 
are phosphorescent. 
ORDER ERRANTIA 
Carnivorous, free Polycheta, with protrusible pharynx armed 
with a horny jaw. ‘They are active, fierce beasts of prey.” 
FAMILY SYLLIDE 
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 APHRODITIDE 
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- 
