80 
MR. W. K. BROOKS ON LUCIFER: 
The last Protozoea stage (Erich thina). 
The change from the last stage to the next one in the series was actually observed 
in several specimens, and more than fifty larvae passed through it in the laboratory. 
After the moult the larva, which is shown from the ventral surface in Plate 4, 
fig. 42, and in outline in fig. 42 a, has the characteristics of Dana’s genus Erichthina. 
Its length, from the tip of the rostrum to the end of the telson, has increased 
to about xooo inch, and most of the increase is in the hind body. The carapace also 
is somewhat elongated (it was a little flattened by pressure in the specimen which 
was drawn), and the outline of the anterior edge is no longer regularly curved. 
At the base of the rostrum there is a slight eminence where the integument is pushed 
out a little by the optic ganglion, and at the outer angle there is a much larger 
eminence which is the rudimentary cornea of the compound eye. The eye itself is 
now represented by a large conspicuous pigment-spot (fig. 42 a, E ). 
The appendages have undergone extremely little change, and they are, as before, as 
follows : the first antennae (A), the second antennae (An), the mandibles ( M ), the two 
pairs of maxillae (Mx. 1 and Mx. 2), and two pairs of maxillipeds (Mp. 1 and Mp. 2). 
The second antennae are still the chief organs of locomotion. 
The hind body is much longer than it w r as at the stage before, and it is now some¬ 
what longer than the carapace. It now consists of nine free segments and an unseg¬ 
mented portion (A 5, 6). The first of the free segments (fig. 42, Mp. 3) is much 
narrower than any of the others, and its outer edges are marked by enlargements 
which appear to be the rudimentary appendages, the third pair of maxillipeds. None 
of the segments which follow it show a trace of the appendages, and the thoracic 
and abdominal ganglia are not yet visible. 
The four segments which follow next after the one with the bud-like processes have 
rounded posterior edges, while the posterior edges of the next four are pointed. The 
later history seems to show clearly that those with rounded edges are the first, second, 
third, and fourth thoracic somites, and that the following ones are the first, second, 
third, and fourth abdominal somites. It will be seen, then, by a comparison of this 
with the earlier and later stages, that the somites of the body are all developed in 
regular order, from in front backwards, but that the first abdominal somite follows 
immediately after the fourth thoracic, while the fifth thoracic is never developed. At 
this stage the long unsegmented region (A 5, 6), represents the fifth and sixth abdominal 
segments and the telson. The two anal pigment-spots are larger than they were 
during the stage before, and from this time to maturity their colour is a dirty reddish- 
brown instead of black. 
The u Zoea” stage (Elaphocaris stage of Sergestes.) 
After the next moult, which was observed in a great number of specimens, the 
larva passes into a stage which is directly comparable, so far as the appendages are 
