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(l. c. p. 265) this Ophiuroid never occurs on Kophobelemnon stelliferum; but outside
the Skagerrak it has been found on Halipteris christii; in fact our Museum possesses
two specimens of the latter sea-pen, resp. from Finmarken and from the Faeroes, each
carrying an Asteronyx.
The Parasitic Copepod in question is apparently a very common parasite in the
interior of Asteronyx loveni, at any rate in the Skagerrak; with very few exceptions I
found it present in every specimen of Asteronyx examined. Some hosts only contained
a few or about a dozen of the parasite, but some were so immensely infested that
their whole interior looked very much like a mass of parasites, and in such cases the
gonads of the host seem not to develop[1]. In most cases ripe and unripe specimens
of both sexes occur in the same host, and in the strongly infested hosts every gradation
as to size and age may be found. It is a true endoparasite, every specimen being
enclosed in the tissues of the host inside the body wall of the latter; only quite
exceptionally — in two cases — I found the parasite visible externally. It is enclosed
in a thin membranous capsule, a kind of “gall” formed by the tissues of the host,
and these galls may be found in every part of the tissues lining the bursal pouches:
on the outer (bursal) walls of the intestinal tract, among the genital sacs, upon the
latter, in the dorsal body-wall; practically in every part of the interior, except inside
the gonads and inside the digestive cavity. In the two cases alluded to above, the
gall was seated so superficially in the dorsal body-wall that its greater part protruded
externally.
The membranous capsule fits tightly round the parasite which generally is distinctly
seen through the transparent membrane. Each gall contains a single parasite in all
cases, where immature specimens are concerned. Very often also the mature male is
found in a gall of its own, whereas galls with a mature female generally also contain
its egg-mass, strongly distending the one end of the sac, and in most cases the largest
galls, containing a ripe female with its brood, also enclose a ripe male (seldom two males),
completely imbedded in the egg-mass, and sometimes empty spermatophores as well.
The eggs do not form “ovisacs” but are only loosely cemented together into one
large mass distending that part of the gall which lodges the posterior end of the
mother. Not only the embryonic development but almost the whole post-embryonic
metamorphosis is performed inside the gall, as will be more fully described below sub II.
I. Description of the developed (imaginal) stages of Chordeuma obesum n. g., n. sp.
The adult female (Pl. I, Fig. 2, 3; 10, 13) is 4—5,3 mm in length,
sausageshaped and clumsy — hence the name I propose for the new genus and species:
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