ANATOMY OF THE EARTHWORM. 145 



c. At about the sixteenth segment, the digestive tract 

 suddenly dilates, and forms a large, muscular, highly 

 vascular, heart-shaped crop (Fig. 84, y), which, in the 

 living animal, usually exhibits muscular contractions, even 

 when the animal has been opened. 



d. Immediately succeeding the crop is the "gizzard" 

 (Fig. 84, g), a firm-walled, cylindrical, highly vascular 

 chamber. 



e. This is followed by the intestine (Fig. 84, /), which 

 passes to the posterior end of the body with very little 

 modification. Its walls are greatly folded and sacculated, 

 especially in the anterior portion. 



/. A layer of brownish-green, delicate, easily-ruptured 

 glands, the hepatic glands, which cover the dorsal surface 

 of the intestine, and surrounding the dorsal blood-vessel, 

 extend as far forward as the oesophagus. 



6. The dorsal blood-vessel. This extends along the 

 dorsal surface of the digestive tract, in contact with its 

 walls, as a distinct vessel (Fig. 84, h], from the poste- 

 rior end of the body to the anterior end of the oesopha- 

 gus, where it breaks up into a number of smaller vessels, 

 which ramify upon the pharynx and oesophagus. 



In the living animal, the mam trunk may be seen to 

 dilate and contract at intervals, but no part of it is modi- 

 fied to form a special pulsating organ. It gives rise, at 

 intervals, to large lateral trunks, which pass outward and 

 downward around the digestive tract to join the infra- 

 intestinal vessel. These arches are very large and promi- 

 nent in the eighth to the thirteenth segments, and are here 

 furnished with small, saccular, pulsatile dilations. 



The dorsal vessel also gives rise to smaller lateral ves- 

 sels, which pass to the muscular partitions, and to the 

 integument and digestive organs. 



