172 



AN INTRODUCTION TO ZOOLOGY 



BLOOD VESSELS. Following a custom, which is so firmly 

 established as to make its abandonment inadvisable, we shall call 

 the blood tubes by the inappropriate name " vessels." Longi- 



FIG. 88. Diagrams showing the arrangement of the blood vessels in the earth- 

 worm. A, longitudinal view of the vessels in somites VIII, IX, and 

 X ; B, transverse section of same region ; C, longitudinal view of the 

 vessels in the intestinal region ; D, transverse section through the 

 intestinal region ; a/. *., afferent intestinal vessel ; c.v., parietal vessel; 

 ef. /., efferent intestinal vessel ; ht., heart ; i, intestine ; it., intestino- 

 tegumentary ; /., lateral-neural vessel ; ces., oesophagus ; s., septa ; sb., 

 ventral vessel ; sn., sub-neural vessel ; sp., dorsal vessel ; ty., typhlosolar 

 vessel. (From Bourne after Benham.) 



