88 THE EARTHWORM. 



In the sheath lie three longitudinal blood-vessels, a sub- 

 neural below the cord, and a pair of lateral neural vessels at 

 the sides. Along the dorsal surface of the cord are three 

 1 giant-fibres ' of nervous nature. The fibrous connective 

 tissue of the sheath extends into the cord, dividing its fibres 

 into two main bundles, and subdividing each of these into 

 smaller ones. Nerve-cells of large size, each with distinct 

 nucleus and nucleolus, form a layer along the whole length 

 of the ventral and lateral surfaces of the cord : they are more 

 abundant in the ganglionic enlargements. 



I. The Blood-vessels. 



These are readily recognised by the deeply stained blood 

 clots with which they are filled. The larger vessels have 

 muscular walls. Besides the neural vessels just mentioned 

 the following may be recognised : 



1. The dorsal vessel lies in the body-cavity above the 



intestine. It is of large size, and has masses of 

 1 hepatic ' cells at its sides. 



2. The intestinal vessels lie in the walls of the intestine : 



they are surrounded by ' hepatic ' cells, and may in 

 some sections be seen to open into the dorsal vessel. 



3. The ventral vessel lies between the nerve-cord and the 



intestine, and is connected with the latter by a 

 median sheet of vascular connective tissue. 



4. The nephridial vessels. 



5. The capillaries of the skin. 



(Esophageal Kegion. 



There is no typhlosole. Sections of the reproductive 

 organs appear and block up the body-cavity. The vesiculse 

 and seminal funnels are especially obvious. 



