40 IOWA STUDIES IN NATURAL HISTORY 
Order Sedentaria—Vegetable feeding Polycheta which permanent- 
ly inhabit tubes. No protrusible pharynx; no jaws or teeth. 
Branchie, when present, usually confined to anterior end and 
sometimes represented by modified tentacles. 
Family Serpulide—Tubes calcareous. 
1. Spirobranchus giganteus. 
2. Pomatostegus stellatus. 
Family Sabellide—Flexible tubes constructed of mud and sand. 
1. Sabella melanostigma. 
2. Dasychone conspersa. 
3. Parasabella sulfurea. 
4. Bispira (Sabella) melania. 
DISCUSSION OF ANNELIDS 
The phylum Annulata contains the highest type of worms. 
They are found in abundance everywhere, some species grow- 
ing to the length of a foot or two. Some are carnivorous, others 
vegetarian, while many are mud-eaters that swallow mud and 
sand to obtain the organisms contained therein. They comprise 
the segmented worms, which number about 4,000 species divid- 
ed into four classes: the Archiannelida, Chaetopoda, Hirudinea, 
and Myzostomida. 
All annulates are bilaterally symmetrical, with head distinct, 
body elongated, digestive tube present, ccelome extensive, ap- 
pendages paired and unjointed. Segmentation is the most 
characteristic feature of the annelids, each segment containing 
a separate and similar set of internal organs. In most annelids 
the head is more or less distinctly marked, containing mouth, 
brain, and sometimes bearing tentacles, cirri, palpi, and eyes. 
Lateral appendages in the annelids are muscular projections of 
the body wall, called parapodia. 
In all annelids except the very lowest a well-developed system 
of blood-tubes, often carrying red blood, is found. The most 
important of these are: a dorsal longitudinal tube just above 
the intestine, a ventral tube just beneath it, and transverse 
tubes connecting the two. The excretory system consists of a 
pair of coiled tubes in each somite, which are called nephridia. 
Each one of these opens into the body cavity at one end and 
carries liquid waste through a nephridial pore to the outside. 
The nervous system consists, in most cases, of a cerebral gang- 
lion, esophageal connectives, and a double ventral nerve-cord, 
