EXPLANATION OF PLATES. 



Abbreviations. 



coel. Coelom, body-cavity. 



eta. Cuticula. 



cta. + e'th. Cuticula and epithelium. 



gl. Gland. 



gnu. Jaw. 



linn. Lemniscus. 



mu. crc. Circular muscle. 



mu. Ig. Longitudinal muscle. 



n. crc. Circular nerve. 



nl. ax. Axial nucleus. 



nl. ba. Basal nucleus. 



n. Ig. Longitudinal nerve. 



n. r. Radial nerve fibre skirting longi- 

 tudinal muscle. 



11. rf Radial nerve fibre passing directly 

 to the membrane superficial to the 

 circular muscles. 



pap. Papilla. 



pi'tn. Peritoneum. 



tis. co'nt. Connective tissue. 



In many figures not only the papilla is shown, but also a portion of the under- 

 lying parts. 



