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embryo somewhat larger, 0,192—0,208 mm. In the same gall may be found newly
laid eggs, eggs in cleavage (the cleavage is total and — at any rate at commencement —
equal) and eggs with embryos in different stages of metamorphosis up to the Cyclopid,
described below. The egg-mass, therefore, probably must be formed of eggs fertilized
and extruded at intervals. Quite generally eggs and free Nauplii will be found together,
whereas I only in single cases have besides found the later stages; that these cases,
however, are quite normal. I do nut 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 (Pl. II, Fig. 14) is ovoid, 0,20—0,21 mm in length, 0,13—0,14 mm
in breadth, with the typical three pairs of appendages and two furcal setæ (c), but
without eyes. The absence of eyes characterizes as well all the following stages.
The antennules (a1) 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 antcnnulæ 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 (a2) 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 almost 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-stage
(Fig. 15) 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 been added:
the maxillulæ (mx1); the remaining limb-rudiments are still only cell-groups, condensed
along the ventral side, below the new cuticle and behind the prominent month. The
nauplial appendages are as before, only the antennules are directed more forwards,
the antennæ and mandibles somewhat ventrally curved.
The dorsal part of the body is more transparent, only one or a few large drops
of oil being prensent in the embryonic entoderm, while the Nauplius-stage had many
small and dispersed drops. The maxillulæ consist each of a large seta terminating a
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