06 ANIMAL PAKASITES AND MESSMATES. 



Histriobdellse, but which is only an imperfectly described 

 Eotator. We believe that it is the same animal to 

 which Professor Grube has given the name of Seison 

 nebalia. It appears to assume the aspect of the Histriob- 

 dellse, and may perhaps be adduced as an example of 

 mimicry. 



The molluscs, whatever their name may imply, are 

 those which show the most independence among all the 

 inferior ranks of animals ; not only are they contented 

 with the slowness of their pace and the wretchedness of 

 their food, but they only very rarely seek help from their 

 neighbours. It is not, however, uncommon to find 

 some living among corals, which have even been desig- 

 nated coralligenous molluscs. There exists a group 

 of Gasteropods, the Eulimae, which lodge in certain 

 Echinoderms, and in every respect deserve to be classed 

 among messmates ; it was a long time before the relation 

 which exists between them and the animals which shelter 

 them had been thoroughly appreciated. Dr. Graffe 

 found one species, the Eulirria brevicula, on the Archaster 

 typicus of the Uvea Islands, in the Pacific Ocean. The 

 molluscs, known by the name of Stylifer, have the same 

 mode of life ; they have been observed in the ABteriae, 

 the Ophiurse, the Comatulse, and even in the Holo- 

 thuriae; and as they inhabit the digestive cavity of 

 these animals, it was believed that they frequented them 

 as parasites. This was the opinion expressed first by 

 d'Orbigny, and adopted by most naturalists. Professor 

 Semper found some in the skin of a holothurian 

 (Stichopus variegatus), which he considered incapable 

 of nourishing themselves otherwise than at the expense 

 of their host. However this may be, these molluscs, 



