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
two pairs of thick ensiform appendages make their appearance at the
opposite end of the body, and behind these a pair of tubercles which are
easily overlooked. These are the antennae and mandibles.
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