THE RINGED WORMS OR ANNELIDS 117 



testine which extends with little modification to the last 

 segment. Attached to the sides of the esophagus, and 

 really consisting of outpocketings of this organ, are the 

 calciferous glands which secrete limy crystalline bodies 

 supposed to neutralize the acids contained in the food. 

 Earthworms swallow dead leaves and other organic sub- 

 stances along with large quantities of soil, and digest what- 

 ever food there may be contained in this material. Rich 

 soil with a considerable proportion of vegetable matter is 

 therefore a favorite haunt for these animals. Absorp- 

 tion probably takes place mainly in the intestine. 



The earthworm has a well-developed circulatory system 

 containing red blood. The principal parts of this system 

 consist of a dorsal vessel extending the length of the body 

 above the digestive tube, a ventral blood vessel running 

 below the intestine, and, lateral vessels extending from 

 these to adjacent parts. The dorsal and ventral blood 

 vessels are connected in front of the crop by five pairs of 

 segmentally arranged vessels which surround the esopha- 

 gus. These are called " hearts" because their pulsations 

 help to propel the blood. The dorsal vessel contracts 

 from behind forward, forcing most of the blood through 

 the hearts into the ventral vessel where it is carried pos- 

 teriorly. 



The earthworm has very odd organs of excretion called 

 nephridia; these are more or less coiled tubes, of which 

 there occurs a single pair in most of the segments of the 

 body. At its inner end, the nephridium is furnished 

 with a ciliated funnel which passes through the anterior 

 septum of its segment to open into the cavity in front. 

 The outer end of the tube opens by a small pore through 

 the side of the body. Waste material swept into the 

 ciliated funnel or secreted by the walls of the tube is car- 

 ried to the outside. 



