84 



an obstruction ; there they rest, and if the situation suits, 

 they fix themselves, if not they move on in the same manner 

 to some other spot. If the change be only for a short 

 distance, as from one part of the leaf to another, they bend 

 their campanulate rims and bring the tentacula in contact 

 with the fucus, and by them adhere to it; the foot-stalk 

 is then loosened, thrown forward, and twirled about, till 

 it meets with a place to suit it; it is then fixed and the ten- 

 tacula are loosened, and in this way they move from one spot 

 to another. They sometimes also move like tiie Actiniae by a 

 gliding motion of the stalk. 



In taking their prey they remain fixed, with their tentacula 

 expatided, and if any minute substance comes in contact with 

 any of the tufts, that tuft contracts, and is turned to the 

 mouth, while the others remain expanded watching for prey. 



The difl'erences between this and Dr. Johnston's specimens 

 are as follows. The brown glandular bodies of the free rim 

 proceed from the tentacula in this, while in Dr. J.'s there is 

 a slight distance between them ; this may arise from the 

 advanced state of the ova in my specimens. In this the chains 

 of glands from the tentacula unite in pairs at three-fourth's of 

 the length of the body ; in the others they proceed singly to 

 the base. In this, the footstalk is distinctly separate from the 

 campanulate rim, in Dr. Johnston's it is said to be sessile, 

 and there is no distinction between the base and the other 

 part. The peduncle, or foot, terminates in a flat, sucker- 

 like expansion while in the other, both in the figures and 

 description, it is absent. These characters have not been 

 observed in a single specimen only, but in scores, and niay 

 therefore be considered permanent variations or characters. 



SUB CLASS II. 



MOLLUSC A IV ZOOPHYTES. 



Body non-contractile, and non-symmetrical; mouth and 

 anus separate ; gemmiparous and oviparous. 



ORDER IV. 

 ASCIDIOIBA. 



In the Ascidian Zoophytes, the Ciliobrachiala of Farrc, 

 we shall observe a very great advance in the complication 

 of tlie anatomy of the polype. Though possessing most of 

 the external characters of the Hydra, and in its oeconomv 

 and fabrication of its habitations also similar ; yet we shall 



