98 
MR. W. K. BROOKS ON LUCIFER : 
appears on its anterior face, and becomes modified in the mature male into the 
clasping organ (fig. 75, c), while a second process (cl) appears a little nearer the tip of 
the limb. 
The second abdominal appendage. 
This appears at the same time with the first, and developes two terminal branches. 
In the mature male a third shorter one is added. 
The third, fourth, and fifth abdominal appendages. 
These all develop at the same time with the first and second; they have two 
terminal branches and are alike in both sexes. 
The sixth abdominal appendage. 
This is present as a rudiment in the last “ Zoea ,” and it becomes fully developed in 
the first Schizopod larva. 
It consists of a basal joint which carries a long, wide, and flat exopodite, and a 
narrower shorter endopodite. 
In the young and in the mature female the outer end of the exopodite is rounded, 
but it is nearly square in the mature male. 
The labrum. 
The labrum is large and conspicuous in the Nauplius , but it has no spine. The 
spine is present from the first Protozoea stage to the last Schizopod stage, but it is 
absent in the adult. 
The compound eyes. 
These make their appearance as rudiments in the last Protozoea, but they are 
not perfectly developed or stalked until the last Schizopod stage. The homology of 
the stalked eyes of the Malacostracan has been a matter of some uncertainty. They 
are usually enumerated in the list of appendages, and the typical Crustacean is sup¬ 
posed to have a corresponding somite. Claus has pointed out (“ Zur. Kenntniss 
der Malacostrakenlarva,” Wiirzb. Zeitschr. ii., 1861. p. 33) that no especial taxonomic 
importance can be attached to their presence or absence ; and their mode of origin in 
Lucifer certainly gives no support to the view that they have been produced, like the 
mandibles, by the gradual specialisation of a pair of ordinary appendages. They do 
not resemble ordinary appendages at any stage, but are formed directly, and the fact 
that the period of their development is spread over several moults renders their 
history quite different from that of the appendages. As I shall show further on, 
