142 



Pao't III. — Tiventy-first Annual Bejjort 



The First Young stage (Fig. 167) has none of the characters of the 

 Megalops. 



The general form of the carapace and pereiopods has changed 

 towards the adult condition ; the lateral teeth of the carapace are now 

 present, though not fully developed. 



The integument is not so transparent as in Megalops ; it now shows 

 some definiteness of structure ; it is not yet calcified. It is, moreover, 

 covered all over the exposed surfaces with minute " needle-point " cilia 

 (Figs. 166, 169). They are amxnged singly, or in groups of two, three, 

 or four. 



The carapace is longer than it is broad. 



The abdomen is tucked in under the thorax^ the five pairs of 

 pleopods are present in a degenerate condition. 



Second, Third, and Fourth (Figs. 173, 170, 171). In the second, 

 third, and fourth stages, with increased bulk, the carapace tends to 

 become broader proportionally. The lateral teeth become more 

 prominent. The eyes become less so. 



The minute " needle-point" cilia were found in ail these stages. In the 

 fourth stage (4 mm.) they were made out on the dorsum of the carapace. 



Crab 5'5 mm. In this crab none of the cilia were found on the 

 carapace. The sexual characters were distinguished at this size. 



The cilia therefore apparently disappear between 4 mm. and 5*5 mm. 



The sexual characters were not noticed in the ciliated individuals : 

 their examination was not, however, an exhaustive one. 



The ciliated stages are probably non-sexual. 



Development of the Appendages. 



The appendages will be considered in the following order: — (1) 

 Antennule, (2) Antenna, (3) Mandibles, (4) First Maxilla, (5) Second 

 Maxilla, (6) First Maxillipede, (7) Second MaxilHpede, (8) Third 

 Maxillipede, (9) Pereiopods, (10) Branchite, (11) Telson, Abdomen, 

 Pleopods, (12) Eye. 



Antennule, a., Plate vii. 



I. (Figs. 2 and 33). The antennule of the first Zoea is 2-jointed, a 

 short proximal and a long distal joint. It is of cylindrical form, and 

 is slightly curved. It bears at its extremity five sensory tubes ; of these 

 two are long, the others short. These tubes are connected directly with 

 the ganglion which is seen occupying nearly the whole of the long 

 joint. When the antennule is examined in situ in the cephalic region 

 (Fig. 33), the short first joint appears to be sunk through the integument 

 into the cephalic region. 



Daring the remaining Zoea stages the number of sensory tubes 

 increases, and the shape of the long joint changes to a pear-shape. 



II. (Fig. 3). The aesthetascs (sensory tubes) are six in number ; 

 of these one is very short, the others vary in length and thickness. 



III. (Fig. 4). In the specimen of the third Zoea, only five aesthetascs 

 were found, but they were arranged differently from the previous 

 stage ; four were terminal, and the fifth arose a little distance short 

 of the tip. 



IV. (Fig. 6). There were now seven sensory tubes; four of these 

 were terminal, and the remaining three arose together a little behind 

 the other group. 



The first joint of the antennule was not noticed. The shape of the 

 long joint has altered considerably, and it is now constricted at its 



