Tae ZooLogist—OcrToser, 1876. 5129 
new shell. There is a similar, though hardly so intimate, connection between 
Pagurus Bernhardus and Sagartia parasitica. This hermit is never found 
without one or more of these anemones attached to the upper surface of its 
habitation, the load sometimes being so heavy that the unfortunate hermit 
can hardly move; but S. parasitica may often be found attached to the 
limbs of Maia squinado, and singly or in clumps to empty univalve shells. 
The extraordinary association of such widely separate animals as crabs and 
anemones is well worthy of more attention than it has hitherto received. 
How do they recognise each other? and, in the case of P. Prideauxii and 
A. palliata, how is it that the young are always found together, and vice 
versd? The benefits of the association appear to be almost entirely in 
favour of the anemone; for it can readily be supposed that, by taking 
advantage of the locomotive organs of the crab, it obtains larger and more 
frequent supplies of food. This is quite in accordance with what has been 
observed in other departments of Nature; but as there is no known instance 
of one species having been created for the sole benefit of another, it is 
probable that there is some compensatory advantage to the crab, and the pains 
which P. Prideauxii takes that the connexion shall not be severed appears to 
point to something of the sort. Can it be that the crab also obtains a 
larger food-supply from, or by means of, the anemone? Anemones never 
digest the whole of what they catch, but, having taken what they need, the 
remainder is thrown up in a round pellet, and, as crabs are scavengers and 
nuisance-removers par excellence, they would have no objection to eat these 
pellets of half-digested food—nay, may possibly consider it a duty to do so. 
Besides the two species above mentioned, other anemones are occasionally 
parasitic. Specimens of Actinoloba dianthus and Sagartia mesembryanthe- 
mum have been seen in this aquarium firmly fixed upon the backs of shore- 
crabs (Careinas menas), and I have myself seen a fine Tealia crassicornis 
completely covering the carapace of a crab of this species. The appearance 
reminded me of a common object of the sea-shore—to wit, a young lady 
mounted on a donkey, his hind legs appearing to belong to his fair burden. 
In Adamsia palliata and Sagartia parasitica the parasitic instinct has 
become permanent, and the structure of the latter species has been 
modified in consequence, for of all the Actinarie it possesses the toughest 
and stoutest skin, which is a manifest protection against the hard knocks it 
must occasionally receive from rocks and stones while moying about at the 
will of its exceedingly active porter. Mr. P. H. Gosse, in his ‘ Actinologia 
Britannica,’ says, “ this association is unaccountable.” Perhaps now that 
these animals can be kept in health and strength in confinement oppor- 
tunities may arise of explaining this, amongst many other unsolved problems 
of marine and freshwater Zoology.—E. Howard Birchall; Crystal Palace 
Aquarium, September 23, 1876. 
