386 MR. LISTER ON THE STRUCTURE AND FUNCTIONS 



larice, except in the resemblance given by their projecting arms, I can discover no 

 more analogy in the Flustrce than in the Ascidice themselves. 



In concluding this desultory paper, I must express my obligation to several of my 

 friends, whose kindness has enabled me to compare my observations in a depart- 

 ment of natural history previously little known to me, with other researches to 

 which I should hardly have found my way alone. 



Explanation of the Fl\tes. 



The numbers with the sign x prefixed denote the linear enlargement. 



Plate VIII. 



Fig. 1. Tuhularia indivisa (page 366.). The arrows show the direction of the cur- 

 rents within. c. The place of their return in the tube. 

 d, e. Nodous parts. 



a. The mouth of the polypus, pressing its fluid contents into the stomach b. 

 a 2. The same on the flow returning from the stomach. 



a 3. The mouth swollen, and the stomach emptied. 

 f. Original end of the shell. 



a 4. The tube and shell extending to the hinder arms, which are in the process 

 of destruction. 

 ao,a6. Appearances at the end of the tube at two later periods. 

 Fig. 2. Sertularia pluma (page 369.). 



X 1. Anastomosis of the creeping tube and manner of growth. 



X 6. A plume. a. Side of the cells. b. Back of the same. 



Fig. 3. Sertularia pumila (page 371.)- ^- Septum in the cells. 



a 2. The same, seen from above by section of the shell. 



b. The aperture in the septum, by which the polypus is connected with the tube. 



c. Mouth of the polypus. d. Stomach. e. Empty ovary. 

 Fig. 4. Sertularia setacea (page 371.)' The soft matter occupies one side of the 



stem, with a current of particles flowing in its axis. 



a. Septum in the small cell. 



b. Spiny ovaries, with the ova indistinctly seen. 



Fig. 5. The minute Sertularia described page 372, with the appendage on the side 

 of its cells. 

 a. Its large ovary, containing an opake mass, connected with the base and 

 end by a column, and with the sides by strings b. 



Plate IX. 

 A young stem of Campanularia dichotoma ? with its annular strictures (page 373.). 

 a. A branch terminated by a perfect polypus. 



