IVREE MESSMATES. 37 



ranged alternately among the Phasianellm, the Turritellse, 

 the Cerithia, the Pyramidellse, the Scalarim, the Ris- 

 soairia, or in a distinct family, seem to belong rather 

 to messmates than to parasites. We meet with Stylifers 

 at the entrance of the mouth (Montacuta) ; more 

 frequently they prefer, like the Fierasfers, to lodge 

 themselves deeply in the digestive cavity in the midst 

 of the debris of the prey. The Melania (M. Cambesse- 

 desii, Eisso), which Delle Chiaie found in the Bay of 

 Naples, on the foot of some comatulse, belongs probably 

 to this group of molluscs. 



Among the gasteropod molluscs which are not able 

 to maintain themselves, we may mention another, a 

 curious parasite, which instals itself in one of the rays 

 of a star-fish, and whose presence is revealed by a swell- 

 ing which is not produced in the other rays. This 

 mollusc has received the name of Stylina. 



The molluscs which are the most remarkable from the 

 point of view from which we are now considering them, 

 are the Entoconchse; they live in Enchinoderms, and it was 

 thought for a while that we could see in them an example 

 of the transformation of one class into another. Some 

 years since J. Muller found in a Synapta from the Adriatic, 

 tubes with male and female organs, without any other 

 apparatus, and in these tubes appeared eggs, whence this 

 great physiologist saw molluscs proceed, with a helicoid 

 shell, similar to that of a small natica ; he gave them 

 the name of Entoconcha mirabilis. Professor Semper 

 has since discovered another species of these, which he 

 has dedicated to the illustrious physiologist of Berlin, 

 and which he found attached to the cloacal sac of the 

 Holothuria edulis. 



