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



peculiar uarrow plate, somewliat expauded 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 pair 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 jcjint or palp is oval, not constricted at the base, 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 

 setse, one very long and reflexed, whereas the three others are directed anteriorl}-. 



The second jiair of maxillge (fig. 17) present a more deviating appearance, being 

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

 long ciliate setse. The terminal joint is lamellar, and oblong in form, and bears at the 

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

 edge of the l>asal 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 apjaearance totally different from those in the adult 

 animal, having more projierly the character of maxilla3 than of legs. They consist of a 

 rather Ijroad and flattened basal jiart, divided into two distinct segments, and of two short 

 tenninal 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 ciliate setje 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 setas. Of an epipodite, no trace whatever can be detected. 



No other limbs are as yet develo2ied, and, with the exception of the antennulse 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) by 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 



