Miscellaneous, 237 



NOTE ON PEDICELLARIA. 



To the Editors of the Annals of Natural History. 



Royal Naval Hospital, Haslar, Aug. 8th. 

 Gentlemen, — The bodies named Pedicellarise found upon the 

 bodies and around the mouths of Echinoderms, have been considered 

 by Oken, Forbes, and Sharpey as special organs of the animals on 

 which they are found. The discovery by myself of a new species (P. 

 volutarum), parasitic on the skin of Voluta vespertilio, will I think 

 confirm the opinion of Cuvier and Miiller, that the bodies in question 

 are independent parasitic organisms. The specimen obtained I have 

 preserved in spirits- I am, Gentlemen, yours very truly, 



Arthur Adams. 



Addendum to Mr. Benson's Paper on Cyclostoma, in the present 

 Number, page 191. 



Dr. Pfeiffer, having examined the original specimen of Cyclostoma 

 Indicum, now writes that it has nothing in common with C. oculus 

 Capri, and that it is distinct also from C. Ceylanicum and stenom- 

 phalum, to both of which it is allied. 



TEREBELLA medusa, by c. spence bate. 



The manner in which this animal proceeds to construct its case is 

 very interesting to watch. By the long feelers or tentacular cirri 

 which surround its head, anything is grasped with which it may 

 come into contact, such as minute shells, grains of sand, &c. These, 

 upon being drawn near, are placed upon its mouth, the lower edge of 

 which forms a prehensile lip. While resting here, it is, I presume, 

 that the glutinous substance, which, when dried, forms the mem- 

 branous lining of the tube, is poured over it. With its lip the crea- 

 ture places the sand upon its back, and then rolls itself over from 

 side to side, and again puts forth its tentacula in search of fresh 

 building material. 



Their tubes are buried in the sand, to the depth of about a foot 

 or more, with one end above and open to the sea, at which extremity 

 minuter ones branch oif, giving it an arborescent appearance. 



The tentacular cirri are hollow, crescent-shaped tubes, which are 

 extended and retracted by the injection into its centre of a fluid sent 

 from the body of the animal. [It is a similar power employed by the 

 Nereid Worms to extend the internal mouth of that family.] When 

 it seizes anything, it does so, I presume, by exhausting the water from 

 the convex side of the crescent-shaped tube, and consequently holds by 

 means of the pressure of the surrounding fluid. 



Within its case the Annelid has the power of moving freely and 

 turning itself at will. Its progressing movement is performed by 

 means of setae, or oars, planted in thick muscular sheaths, which 

 enable it to pass freely in one direction, but which, being directed 

 backwards, wholly preclude a retrograde movement. The mechanism 

 by which this latter power is executed, is by means of a long row of 

 minute triple-pointed hooks situated at the base of each set of setae ; 



