Hector F. E. Jungersen: Chordeuma obestun, a new Parasitic Copepod. 13 



embryo somewhat larger, 0,192 — 0,208 mm. In the same gall mav be found newly 

 laid eggs, eggs in cleavage (the cleavage is total and — at any rate at commencement — 

 equal) and eggs with embryos in difterent stages of metamorphosis up to the Cyclopid, 

 described below. The egg-mass, therefore, probably must be formed of e^s fertilized 

 and extruded at intervals. Quite generally eggs and free Nauplii will be found together, 

 whereas 1 only in single cases have besides found the later stages; that these cases, 

 however, are quite normal, I do not doubt, and I take it for granted, that the regular 

 methamorphosis is intracapsular and always will show the series a — e described below. 



a. The Nauplius (PI. 11, Fig. 14) is ovqid, 0,20—0,21 mm in length, 0,13—0,14 mm 

 in breadth, with the typical three pairs of appendages and two furcai setæ (c), but 

 without eyes. The absence of eyes characterizes as well all the following stages. 



The antennules (ai) are three-jointed, the basal joint short, the terminal one 

 long (the segmentation is, however, very feebly pronounced, and the number of joints 

 rather difficult to settle). Terminally the antennulæ have three setæ, one short, two 

 longer and stronger; the middle joint has, ventrally, one long seta, the basal joint 

 one, somewhat shorter and feebler. The antennæ (a,) possess two indistinctly jointed 

 branches; the shaft is probably composed of two joints (without "masticatory process"); 

 the outer branch is the longer and stronger and seems to be many -jointed; distally it 

 Carries five strong setæ (each probably marking a joint); the inner branch seems two- 

 or three-jointed, has terminally three setæ, one short and two long and strong ones. 

 The mandibles (md) have al most the same structure, only the outer branch has 

 (generally) but four setæ. There are no plumules on the setæ nor on the caudal setæ. 



Through the arched dorsal body-wall the large brain is distinctly seen, as are the 

 strong muscles going to the appendages. On the ventral side — or better in profile 

 — is seen a prominent hunch on which — later — the mouth-opening is found. 



Inside the nauplial cuticle the differentiation of several organs takes place. From 

 the ectoderm the ventral nervous system originates together with the rudiments of four 

 postoral pairs of limbs. The cuticle is cast, and b) the first Metanauplius-stagp 

 (Fig. 16) ensues. It resembles the Nauplius, only the body is a little more lengthened; 

 the size is about the same, ca. 0,208 — 0,224 mm in length, 0,136 mm in breadth; but 

 in addition to the three pairs of appendages one pair of free limbs has heen addedt 

 the max il lu læ (mx'); the remaining limb-rudiments are still only cell-grojups, condensed 

 along the ventral side, below the new cuticle and behind the prominent mouth. The 

 nauplial appendages are as before, only the antennules are direeted more fonvards, 

 iho antennæ and mandibles somewhat ventrally curved. 



The dorsal part of the body i» more transparent, only one or a fow Jar^jf <lri'|t> 

 of oil being present in the embryonic ontoderm, while the iNauphus-stagi* had iiiuny 

 small and dispersed drops. The maxillulæ consisl each of a le^rge seta terminaling a 



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