98 MR. W. K. BROOKS ON LUCIFER: 



appears on its anterior face, and becomes modified in the mature male into the 

 clasping organ (rig. 75, c), while a second process (d) 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 '' Zoca" 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 labrurn. 



The labrum is large and conspicuous in the Nauplins, 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. GLAUS has pointed out (" Zur. Kenntniss 

 der Malacostrakenlarva," Wiirzb. Zeitschr. ii., 180 1. 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, 



