94 MB. W. K. BROOKS ON LUCIFER: 



pointed out (' Untersuchungen,' &c., p. 15), that the Decapod metastoma is moi*pho- 

 logically a pair of appendages ; that it has been formed by the simplification and union 

 of structures homologous with the limbs; and that this pair of appendages was originally 

 furnished with a body-somite and a pair of ganglia. CLAUS'S reason for the homology 

 is the resemblance between the Decapod Protozoca, and the larva of Phyllopods and 

 Copepods, and the manner in which these parts are developed in the Nauplii of Lvcifer 

 and Eitphausia seems to be an additional reason for accepting his view. 



The first maxilla. 



This appendage is rudimentary during the Nauplius stages, but, as shown in 

 fig. 21, MX. 1, it is represented by a pair of buds several hours before birth. 



In the Protozoea and Zoea series it has the form shown in fig. 46, which was drawn 

 from the appendage of a larva in the last Zoea stage. Its characteristics are developed 

 gradually, and it is somewhat simpler during the earlier Protozoea stages than it is in 

 fig. 4(3. Fig. 30 shows it as it appears in the first Protozoea when seen from the 

 outside. It consists of a basal portion (fig. 46) made up of two joints (1 and 2), which 

 carries a short obscurely-jointed endopodite (en) and a scaphognathite (.*). In my 

 description of this and the other mouth parts of Lucifer I have accepted CLAUS'S 

 homology ('Untersuchungen,' &c., p. 16), and regard the two basal joints as the 

 equivalent of the basal portion of the antenna, or of one of the thoracic limbs ; the 

 jointed palpus as the homologue of the inner ramus of the antenna, or the limb proper 

 of one of the thoracic appendages ; and the scaphognathite as the homologue of the 

 exopodite of one of the thoracic appendages, or of the antennte. In all these appen- 

 dages the exopodite is shorter than the endopodite, unjointed, and set with long hairs, 

 the plumose character of which is well marked. The scaphognathite of the maxilla 

 agrees with the exopodite of the second antenna and of the other appendages in this 

 respect, while the palpus of the maxilla agrees with the endopodite of the second 

 antenna, and with that of the mandible of the JVfmj;>?n<sand with the thoracic limbs of 

 the adult Lucifer, in consisting of several joints with one or more, usually simple, 

 hairs at each joint. 



The inner edges of the basal joints of the maxilla, carry cutting hairs, and the 

 second joint is largest. The endopodite carries five long slender hairs which are simple 

 in the earlier and plumose in the later stages. The scaphognathite carries three hairs 

 which are equal and simple in the earlier Protozoea, but plumose in the Zoca, where one 

 is very much longer than the other two. 



The structure of this appendage undergoes extremely little change from the time it 

 appears in the Protozoea to maturity. In the Schizopod larva (fig. 52) the second 

 basal joint (2) has become much larger than the first (1), and its cutting hairs are more 

 numerous than before ; a small slender plumose hair has made its appearance on the 

 edge of each joint. The endopodite (en) is obscurely three-jointed, and the scaphogna- 

 thite (sc) has only two long plumose hairs. 



