76 
MR. W. K. BROOKS OK LUCIFER : 
in its dorsal wall into a small rounded anterior chamber, into which the oesophagus 
opens, and a longer posterior chamber, with its dorsal wall very thick, which gives 
rise at its posterior end to the intestine (i). The greater part of the anterior chamber 
lies in front of the oesophageal opening. On each side of the stomach there is a group 
of polygonal yolk-cells (/), which are by no means as conspicuous as they were at an 
earlier stage. The intestine is small, with thin walls, and it follows the dorsal curva¬ 
ture of the body to the anus, which was visible in a ventral view just in front of the 
spines of the telson, at the point marked (a) in fig. 26. The cerebral ganglia {get), 
and the ocellus (oc), are still visible, and underneath the stomach there is an elongated 
granular body (n), obscurely divided into segments, which is, without doubt, the rudi¬ 
mentary ventral nervous system. 
As it was necessary to keep this larva alive I did not dare to use much pressure 
whilst examining it, and was therefore unable to make a very thorough study of its 
internal structure. 
The first Protozoea stage. 
On Tuesday evening, September 28th, at 9.30 p.m., the Nauplius which has just 
been described was placed alone in a watch-glass of sea-water, and at 9 a.m. on 
Wednesday, the 29th, it had changed into the larva which is shown in dorsal view in 
Plate 3, fig. 27. The number of segments and appendages of this larva and its 
general form and proportions are like those of the Euphausia , Penceus, and Sergestes 
larvae at the stage of "development which Claus has proposed to call a Protozoea 
(‘Crustacean System/ p. 2). The precise time when the change took place could not be 
learned, but there is reason to believe that it was not much later than the middle of 
the night. On September 14th I obtained, by dipping with a surface-net, a Protozoea , 
which I studied and drew. It was of exactly the same size (totto of an inch measured 
from the tip of the rostrum to the bases of the spines of the telson) as the one which 
moulted from the Nauplius , and it agreed with this in every respect except that the 
free segments of the hind body, shown in fig. 27, were wanting. It hardly seems 
probable that there are two stages of exactly the same size between 9.30 p.m. 
and 9 A.M., and it is much more probable that the body segments do not become 
distinct until some time after the moult, and as the larva had them at 9 a.m., I infer 
that it was nearer the end than the beginning of the first Protozoea stage, and that 
the change had taken place some hours before I examined it. 
Claus is inclined to believe that the difference between Fritz Muller’s last figure 
of the Nauplius of Penceus and his first figure of the Protozoea is so great that there must 
be a gap in the series of observations. The isolated Nauplius of Lucif 'er passes through 
quite as great a change in twelve hours, and its length increases from xwo room 
or more than 100 per cent., and there does not seem to be any necessity for supposing 
that Fritz Muller has missed a stage in order to account for the change in his 
larva. 
