/ 



282 EXPLANATION OF THE PLATES. 



Cercarice : a oesophogeal csecum, or rudiment of an alimentary. 

 canal. This is really the second of the redial forms figured by 

 Steenstrup. 



Fig 10, — Cercaria, or larva form of the Distovna, being one of 

 the brood figured in the last. 



Fig. 11. — Ultimate form of Distom,a, produced by a transfor- 

 mation of the last during its stage of encystment. 



Fig, 12, — Myrianida fasciata from M, Edwards — showing the 

 formation of caudal zooids, as described at page 101. 



