1864. | Zoology and Physiology, 173 
relations existing between tho Crab, Pagurus Prideauxii, and the 
Zoophyte, Adamsia palliata. These two incongruous animals are, it 
is well known, constantly found associated together, and although we 
have found them difficult to keep alive in an aquarium, Lieut.-Col. 
Stuart Wortley has been more successful, and has observed the crab, 
after eating two pieces of meat given to it, seize a third with its large 
claw, and thrust it into the expectant mouth of the Adamsia. This 
has been frequently repeated. On leaving its shell, for the purpose 
of establishing itself in a new one, the Pagurus returned to the old 
shell, and dislodged the Adamsia with its pointed claws, during which 
rough process no acontia were thrown out, as would be done on the 
slightest irritation from any other source ; and when entirely separated, 
the crab holds it firmly with its base against the new shell until it has 
affixed itself. It remained on one occasion for an hour in this position, 
when, finding Adamsia did not affix itself readily, it returned to its old 
shell upon which Adamsia firmly attached itself as before. So attached 
does the crab appear to be to its helpless companion, and so loath to 
quit its hold upon it, that Col. Wortley concludes, as we were inclined 
to do from facts observed in dredging when they were abundant, that 
Adamsia palliata is almost, if not quite, a necessity of existence to 
Pagurus Prideauxii. The converse, however, cannot be said, for we 
have kept a specimen of Adamsia alive for twelve months unattached 
to any shell, the Pagurus having died on the day succeeding its capture. 
Another remark on the habits of Crustaceans has been furnished by 
Mr. Moore, Curator of the Liverpool Museum, in reference to the King 
Crab (Polyphemus) of which several living specimens have been sent 
over by Professor Agassiz. The long spine-like tail of this species 
has excited much question as to its use. If they are turned over on 
their backs, they bend down the tail until they can reach some point 
d’appui, and then use it to elevate the body and gain their normal 
position. The function assigned to it by some, viz. of placing it under 
the body and leaping from place to place, has never been observed. 
Rudolf Leuckart has made some interesting observations upon the 
development of the Acanthocephali, the only group of Entozoa whose 
development had hitherto eluded the investigations of naturalists. 
Scattering the ova of six or eight Hchinorhynchi of the species HE. pro- 
teus in a bottle containing Gammari, he found in a few days a great 
number of these ova in the intestines of the Gammari. The embryos 
quitting their envelopes passed into the abdominal cavity of the Crus- 
taceans. After three or four weeks the embryo underwent a singular 
metamorphosis, which converted its nucleus into a true Echinorhynchus, 
like an Echinorderm in its Pluteus. This rapidly increases in size, 
and finally fills the body of the embryo, which becomes transformed 
into the envelopes external to the muscular tube of the worm, and dis- 
tinguished by a proper vascular system. When the spinous armature 
of the head is formed, it draws back into the posterior part of its body 
like a Cysticercus in its vesicle. Leuckart has counted fifty or sixty 
parasites in a single Gammarus. 
Considerable attention has been devoted to the characters of the 
