6 MR. W. K. BROOKS ON 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 cesophageal 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. 2G. The cerebral ganglia (go), 

 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, Pcnceus, and Sergestes 

 larvae at the stage of 'development which GLAUS 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 1 4th I obtained, by dipping with a surface-net, a Protozoea, 

 which I studied and drew. It was of exactly the same size (TTO f 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 Naiyjlius, 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. 



GLAUS is inclined to believe that the difference between FRITZ MULLER'S last figure 

 of the Nauplitis 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 Lucifer passes through 

 quite as great a change in twelve hours, and its length increases from 10 9 00 to Y^J, 

 or mure 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, 



