FREE MESSMATES. 49 



Professor Mobius, as well as Dr. F. Martens, has 

 noticed a Ilcmieiiryale pustulata on a polyp of Jamaica, 

 known under the name of Verriicella Guadelupensis, This 

 is a curious instance of mimicry. 



The class of polyps includes several species which 

 seek for assistance from others, and are classed among 

 messmates. One of the most remarkable is the Gigantic 

 Medusa, which can extend its arms downwards to a 

 hundi'ed and twenty feet, and bears the name of Cyanea 

 arctica; the disc is seven feet and a half in diameter, 

 and when the animal is on the surface of the water, the 

 fringes, which surround the cavity at its mouth, occa- 

 sionally afford lodging in the midst of them to a species 

 of actinia, which lives there as messmate. Sometimes 

 three, and even four or five, are found on a single Cyanaea. 

 This also is an observation due to Mr. A. Agassiz, 

 which he has published in his interesting work, " Sea-side 

 Studies." Prof. Haeckel supposed that the Geryonise 

 produce CEginidse by means of buds ; but it appears 

 that the learned professor was mistaken as to the 

 nature of these buds; that instead of being produced 

 one from the other, they have, according to Steenstrup, 

 a completely different genealogy, being only united by 

 conditions of good-fellowship. They may be truly called 

 messmates. 



Mons. Lacaze-Duthiers, who went to the coast of Africa 

 to study corals, met with a young polyp which requires 

 the assistance of another polyp in its early condition. 

 This animal, to which he has given the name of Gerardia 

 Lamar ckii, lives on one of the Gorgonia3, which it invades 

 and stifles, as the lianas strangle the tree over which 

 they spread themselves. But these same Gerardiaj can 



