1^34 THE VOYAGE OF H.M.S. CHALLENGER. 



peculiar narrow ]»late, somewhat expanded at the extremity, and having the apical edge 

 finely denticulate. This plate (fig. 15), wanting entirely in the adult animal, would 

 appear to be movably connected with the mandible, since it is very easily disengaged. 



The first paii' of maxillae (fig. IG) exhibit all the parts observed in the adult animal, 

 though they are of a somewhat dissimilar form and armature. Of the two masticatory 

 lobes, the inner lobe is linguiform, and furnished with eight strong ciliate bristles, 

 whereas the outer is truncate at the extremity, and armed with only two thick, digitiform 

 spines ciliate at the tip, exclusive of a simple bristle originating between the spines. The 

 terminal joint or palp is oval, not constricted at the liase, and provided with six bristles, 

 three of which spring from the tip, and three from the inner edge. The exognath is 

 very small, forming only a minute knob-like projection furnished with four strong ciliate 

 setae, one very long and reflexed, whereas the three others are directed anteriorly. 



The second pair of maxillae (fig. 17) present a more deviating appearance, being 

 rather narrow, with the inner edge divided into five small rounded lobes, provided with 

 long cihate setae. The terminal joint is lamellar, and oblong in form, and bears at the 

 rounded tip four curved setae. Of a distinct exognath no trace can be found, the outer 

 edge of the basal part being not in the least expanded, and furnished only at the distal 

 part with a single ciliate bristle. 



The maxillipeds (fig. 18) are in appearance totally different from those in the adult 

 animal, having more properly the character of maxillae than of legs. They consist of a 

 rather l)road and flattened basal part, divided into two distinct segments, and of two short 

 terminal branches, the inner representing the endopodite, the outer the exopodite. The two 

 segments of the basal part (the coxal and basal joints) have their inner edges somewhat 

 expanded and setiferous, four slender cihate setae springing from the proximal segment, 

 and four shorter ones from the distal Moreover, a minute spine occurs between the two 

 outermost setae of the distal segment. The endopodite scarcely exceeds half the length 

 of the basal part, and consists of two well-defined joints ; the proximal is broader than 

 long, and bears at the inner edge a short spine and a ciliate bristle, whereas the distal 

 joint is ovate, and provided at the tip with four slender curving setae. The exopodite is 

 about the same size as the endopodite, but consists of only a single oblong joint, bearing 

 four slender apical setae. Of an epipodite, no trace whatever can be detected. 



No other' limbs are as yet developed, and, with the exception of the antennulae and 

 antennae, they all serve, as true oral organs, for conveying food to the mouth. 



Second Calyptopis Stage (figs. 20-22). — In this stage the larva has a length of 1^ mm., 

 and is chiefly distinguished (see fig. 20) Ijy a more perfect development of the tail, which 

 has now fully attained the length of the carapace, and is also divided into seven distinct 

 segments. The last of these, representing the telson (fig. 22), is somewhat spathulate at 

 the end, and exhibits along the edge an armature similar to that in the preceding stage, 

 except only that an additional spine has appeared in the middle of the apical edge, and 



