LUMBRICUS 



151 



to other neurons and eventually to muscles. A bundle of axons 

 passing out to a muscle is called a motor peripheral nerve. 



A transverse section of an earthworm, such as can be cut by a 

 microtome from a specimen embedded in paraffin wax, is most 

 instructive, in exhibiting the relation to one another of the various 

 tissues which make up the body of the earthworm. The outermost 



16 



Fro. 63. Transverse section through Lumbricus terrestris in the region of the 

 intestine and of a dorsal pore. Magnified. 



1. Cuticle. 2. Ectoderm or epidermis. 3. Circular muscles. 4. Dorsal 

 nerve. 5. Longitudinal muscles. 6. Parietal peritoneum. 



7. Visceral peritoneum or yellow cells* 8. Endoderm or epithelium 

 lining the intestine. 9. Coelom. 10. Nephridium cut in section. 

 11. Dorsal pore. 12. Dorsal blood-vessel lying along the typhlosole 

 or groove in the wall of intestine. 13. Sub-intestinal blood-vessel. 



14. Ventral nerve-cord. 15. Sab-neural blood-vessel. 16. Ventral nerve. 



The dorsal and ventral nerves are added diagrammatically. The other 

 structures are drawn from nature. 



boundary is constituted by the cuticle (1, Fig. 63), a hardened 

 secretion poured out by the ectoderm (2, Fig. 63). The ectoderm 

 is composed of tall cylindrical cells, amongst which are isolated 

 " goblet cells "that is, cells with a round body situated beneath 

 the level of the rest and with a long neck. The name is 

 suggested by their shape. In the body of these cells mucus is 



