ANIMAL PARASITES AND MESSMATES. 



675 



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surface of their skin, where the tiny creatures iix themselves by means 

 of strong cables. Fig. 7 represents a species that lodges on the cod, 

 and it in its turn aftbrds a resting-place for another form the Udo- 

 nellce. 



A curious creature, with an equally curious 

 function, that entitles it to a place among mu- 

 tualists, was discovered some years ago among 

 the eggs of the lobster, by Van Beneden, who 

 thus describes it : " It is known that lobsters, as 

 well as crabs, and the greater part of the Crus- 

 tacea, carry their eggs under the abdomen, and 

 that these eggs remain suspended there nntil 

 the embryos are hatched. In the midst of them 

 lives an animal of extreme agility, which is, per- 

 haps, the most extraordinary being that has been 

 subjected to the eyes of the zoologist. It may 

 be said, without exaggeration, that it is a biped, 

 or even quadruped, worm. Let us imagine a 

 clown from the circus, with his limbs as far dis- 

 located as possible, we might even say entirely 

 deprived of bones, displaying tricks of strength 

 and activity, on a heaj) of monster cannon-balls 

 which he struggles to surmount ; placing one 

 foot, formed like an air-bladder, on one ball, the 

 other foot on another, alternately balancing and 

 extending his body, folding his limbs on each 

 other, or bending his body upward like a cater- 

 pillar of the Geometridce, and we shall then have 

 but an imperfect idea of all the attitudes which 

 it assiimes, and which it A^ai"ies incessantly. It 

 is neither a parasite nor a messmate ; it does not 

 live at the expense of the lobster, but on one of 

 the productions of these crustaceans, much in 

 the same manner as do the Callgi and the 

 Argidi. The lobster gives him a berth, 

 and the passenger feeds himself at the 

 expense of the cargo ; that is to say, he 

 eats the eggs and the embryos which die, 

 and the decomposition of which might 

 be fatal to his host and his progeny. 

 These HistriohdellcB have the same duty 

 to perform as vultui-es and jackals, which clear the plains of carcasses. 

 That which causes us to suppose that such is their appropriate office 

 is, that they have an apparatus for the purpose of sucking eggs, and 

 that we have not found in their digestive canal any remains which 

 resemble any true organism." 



Op the Nat- Caligulus ELEaANS. 



URAL Size. 



Fig. 7. 



Female. 



