8 



EARTHWORMS AND LEECHES 



[CH. I 



animals. A somewhat similar typhlosole is found in the 

 intestine of fresh-water Mussels, though here it is accom- 

 panied by a few convolutions. 



10 



10 



Fig. 3. 



Transverse section through Lumbricus terrestris in the region of 



the intestine, and of a dorsal pore. Magnified. 

 Cuticle. 2. Ectoderm or epidermis. 3. Circular muscles. 



4. Dorsal nerve. 5. Longitudinal muscles. 6. Somatic 



epithelium. 7. Splanchnic epithelium or yellow cells. 8. Epi- 

 thelium lining the intestine. 9. Coelom. 10. Nephridium 

 cut in section. 11. Dorsal pore. 12. Dorsal blood vessel 

 lying along the typhlosole or the groove in the wall of the intestine. 

 13. Subintestinal blood vessel. 14. Ventral nerve cord. 15. Sub- 

 neural blood vessel. 16. Ventral nerve. 



The dorsal and ventral nerves are added diagrammatically. The other 

 structures are drawn from nature. 



The spiral valve that occurs in the intestine of the 



