4 Mindeskrift for J.Steenstrup. XVI. 



(1. C. p. 265) this Ophiuroid never occurs on Kophobelemnon stelliferum; but outside 

 the Skagerrak it has been found on Halipteris christii; in faet our Museum possesses 

 two specimens of the latter sea-pen, resp. from Finmarken and from the Faeroes, each 

 carrying an Asteronyx. 



The Parasitic Gopepod 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 thai 

 their whole interior looked very much Hke a mass of parasites, and in such cases the 

 gonads of the host seem not to develop ^). 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. 



1. Description of the developed (imaginal) stages of Chordeuma obesum n. g., n. sp. 



The adult female (PI. I, Fig. 2, 3; 10, 13) is 4 — 5,3 mm in length, sausage- 



shaped and clumsy — hence the name I propose for the new genus and species: 



^) In some hosts a parasitic Nematode — resembling a small Ascaris — was found together 

 with the Crustacean. 



