EXPLANATION OF THE PLATES. 



PLATE I. 



Fig. 1. J'ljrosoiuu cxjassizi, shows the open end of the colony, with the four processes around 



the orifice. 

 Fig. 2. " " tlu'ee nearly adult zooids, looked at on the posterior side; /. e., 



the side of the atrial orifice, and each with a stolon and two 



younger zooids. 

 Fig. 3. " " a single zooid seen from its right side. 



Fig. 4. " '* the intestinal tract, with a portion of the branchial sac, and of the 



posterior end of the eudostyle. 

 Fig. 7. " '' liie atrial tentacle and the atrial sphincter muscle, with its groups 



of nuclei. 



PLATE II. 



Fig. .5, Pi/roHoma (irjassizi, the circle of branchial tentacles, showing the larger ventral one. 

 Fig. 6. " " the ganglion and hypophyseal gland and adjacent structures, 



seen from the inside. 

 Fig. 8. " " an enlarged view of one of the groups of nuclei of the atrial 



sphincter muscle. 

 Fig. 9. Oikoj/lpiira Imxlei/i^ the body of the animal, seen from the right side. 

 Fig. 10. '■ '• the intestinal tract and gonad, seen from the ventral side. 



¥\^. 11. " " the tail. 



