PAPERS OX BIOLOGY AND AGRICULTURE S3 



from the alimentary tract through branches of the 

 cular system in each of most of the somites. This blood 



- anteriorly and is forced into the ventral vessel by 

 the hearts. In the anterior dozen somites the 



not function as a collecting vessel. The vent- 

 ral vessel is in general a distributing ssel in it 

 blood is distributed to the body wall and alimentary 



t. In it the blood flows anteriorly in front of the 

 steriorly throughout the remainder of the 

 body. It is a very common assumption by text-book 

 authors that the dorsal vessel fnncti is s a collecting 

 aghOnt its whole extent, which is not true. 

 Two longitudinal vascular trunks lying one on each side 

 of the alimentary canal, and joining the dorsal vessel at 

 their posterior ends in the twelfth somite, act as the 

 collecting vessels in the anterior somites in place of the 

 dorsal vessel. Only seven of the text-books mentioned 

 make any reference to these vessels, and only one of 

 them makes reference to the posterior connection- : 

 these vessels with the dorsal vessel in somite 12. Very 

 few of the authors seem to have known of a very useful 

 paper on circulation in earthworms which appeared in 

 The American Naturalist in 1902 and was prepared by 

 Johnston and Johnson. 



