Still
more remarkable is a similar circumstance in Caligus, among the
parasitic Copepoda. The young animal, described by Burmeister as a
peculiar genus, Chalimus, lies at anchor upon a fish by means of a cable
springing from its forehead, and having its extremity firmly seated in
the skin of the fish. When sexual maturity is attained, the cable is
cut, and the adult Caligi, which are admirable swimmers, are not
unfrequently captured swimming freely in the sea. (See 'Archiv. fur
Naturgeschichte' 1852 1 page 91).)
(FIGURES 44 TO 46. Feet of a half-grown Hyperia Martinezii, n. sp.
(Named after my valued friend the amiable Spanish zoologist, M.
Francisco de Paula Martinez y Saes, at present on a voyage round the
world.)
FIGURES 47 TO 49. Feet of a nearly adult male of the same species; 44
and 47 from the first pair of anterior feet (gnathopoda); 44 and 48 from
the first, and 46 and 49 from the last pair of thoracic feet. Magnified
90 diam.)
Thus, in order to give a few examples, the powerful chelae of the
antepenultimate pair of feet, of Phromina sedentaria, are produced,
according to Pagenstecher, from simple feet of ordinary structure; and
vice versa, the chelae on the penultimate pair of feet of the young
Brachyscelus, become converted into simple feet. In the young of the
last-mentioned genus the long head is drawn out into a conical point and
bears remarkably small eyes; in course of growth, the latter, as in most
of the Hyperinae, attain an enormous size, and almost entirely occupy
the head, which then appears spherical, etc.
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