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sites, one on each side of the anterior division of the body, both turning their
heads towards that of their host (see fig. 1). On examining the specimens more
closely, they were found to be of rather different size and different degrees of
development, though evidently representing the very same species. The smallest
specimens (fig.
1 a) had all the characters of a normal Bopyrid-larva in the 1st
stage, and exhibited a strong resemblance to the well-known larva of Phryxus
abdominalis (cf. PL 91 below), the number of legs being only 6 pairs, and
the antennse, pleopoda and uropoda being tipped with slender bristles. In some-
what larger specimens (fig. 16) the antennse had lost their bristles, and assumed
the appearance characteristic of the Mieronisci, looking merely like simple inarti-
culate processes. The 6 pairs of legs exhibited likewise a much more clumsy
appearance, showing scarcely any trace of articulation, though terminating in a
sharp hook-like point, and behind them a 7th pair of legs was seen in process
of formation as 2 comparatively small rounded tuberosities. The pleopoda were
still tipped with bristles, but of very small size, whereas the uropoda were wholly
devoid of such bristles, and their rami were only present in the form of slight lobes.
In other specimens (fig.
1 c.) of larger size and with the body more produced, the
7th pair of legs had lengthened considerably so as to project laterally, though
showing as yet no trace of a terminal claw (see fig.
1 c., p 7). In this
stage, which otherwise did not difier much from the preceding one, the
Microniscus agrees rather closely with one of the 2 specimens recently figured
by Dr. Hansen in his work on the Isopoda, Cumacea and Stomatopoda of the
German Plankton-Expedition. Finally, in the largest specimens (fig.
1 d), which
exhibited all the characters of a normal Microniscus calani, all the 7 pairs of
legs were distinctly developed and of exactly the same structure, representing
indistinctly articulated grasping organs, (fig.
1 d. p.), and the uropoda had leng-
thened considerably, the outer ramus projecting far beyond the inner, and exhibiting
a -few small hairs at its tip (see fig.
1 d. urp.). In all the specimens, distinct
though rather small eyes were present on each side of the flat, semicircular
cephalon, and the lateral parts of the segments were more or less acutely pro-
duced, giving the sides of the body a jagged appearance.
Another form of Microniscus was found in a different locality, clinging
to a deep-water Calanoid, Mdridia longa Lubbock (fig. 2). This form (fig. 2 a),
of which 2 specimens were secured, agreed
in all essential characters with that
found on Pscudocalanus doiujatu*, but was of somewhat larger size, and had the
lateral parts of the segments less produced. It differed, moreover, in the total
absence of visual organs, as also in the structure of the uropoda. \YluTeas in
the other form, the inner ramus of these appendages exhibited a very rudimen-