of the antennae leads to the supposition that they belong to our
commonest Prawn, which is very frequently eaten, and is most nearly
allied to Peneus setiferus of Florida. Claus's Acanthosoma (l.c. Figure
13) is like the younger Mysis-form of the larva figured by me in the
'Archiv fur Naturgeschichte,' 1836, Taf 2, Figure 18, and which I am
inclined to refer to Sicyonia carinata.)

The youngest larva of the Schizopod genus Euphausia observed by Claus,
stands very near the youngest Zoea of our Prawns; but whilst its
anterior antennae are already biramose, and it therefore appears to be
more advanced, it still wants the middle maxillipedes. In it also Claus
found the heart furnished with only a single pair of fissures. Do not
Nauplius-like states in this case also precede the Zoea?

(FIGURE 33. Older larva produced from the Zoea represented in Figure 32.
The last segment and the last two pairs of feet of the middle-body are
wanting. Magnified 20 diam.)

The developmental history of Mysis, the near relationship of which with
the Shrimps and Prawns has recently again been generally recognised, has
been described in detail by Van Beneden. So far as I have tested them I
can only confirm his statements. The development of the embryo commences
with the formation of the tail! This makes its appearance as a simple
lobe, the dorsal surface of which is turned towards and closely applied
to that of the embryo. (The young of other Stalk-eyed Crustacea are, as
is well known, bent in the egg in such a manner that the ventral
surfaces of the anterior and posterior halves of the body are turned
towards each other,--in these, therefore, the dorsal, and in Mysis the
ventral surface appears convex.) The tail soon acquires the furcate form
with which we made acquaintance in the last Prawn-Zoea described. Then