Report on Larval Crahs. 15 



was a mass of dark brown tissue. The eyes were of a bright silver on the 

 outer surface. Red pigment was located deep in the eye. A dark brown 

 tracing is present on the side of the carapace and extending down the 

 abdomen. In an early stage the red pigment was not nearly so prominent, 

 and below the dorsal spine there was a large mass of yellow pigment. 



Generally there is an extensive chocolate-coloured area round the 

 stomach. It may be very dark, almost black. In one larva, however, the 

 chocolate colouration was absent. The Zoea otherwise resembled the 

 others, and was very lively. 



A number of specimens became whitish in appeai^ance. All the chocolate- 

 coloured pigment in the cephalothorax disappeared. It was succeeded by 

 a whitish tinge. This may have indicated a prepai-ation for casting. Some 

 of those, however, which were moulting had the chocolate-coloured area. 



When about to cast the sides of the carapace spread out laterally ; this 

 gives a greater size to the larva. The Zoea first withdraws the abdomen. 

 The pereiopods come out as soon as the carapace is raised. The carapace is 

 pushed over the head, the eyes and the appendages being the last to be 

 shed. In some the abdomen appears to be last, but only rai^ely, if at all, 

 in normal circumstances. Some Zoea? which had commenced moulting had 

 not finished the operation a day later. 



Plankton Zoene. 



The youngest Zoea was that shown in fig. 71. I regard it as a II. Zoea. 



It has four 6et« on the exopodites of the first and second maxUlipedes. 



The abdomen consists of five segments and the telson. The pleopods are 

 represented by conical swellings on the lower surface of the abdomen. The 

 little stud is present on the third segment. 



The telson (fig. 80) is narrow, resembling generally the telson of the 

 I. Zoea. There are three teeth on each prong — two, a large and a small 

 tooth, on the outer edge, and a large tooth on the dorsal surface. The 

 prongs are minutely seiTated. The middle spine on each side of the fork 

 was larger than the spines flanking it. 



This .stage cast into HI. Zoea. 



///. Zoea. Fig. 1. 



The exopodite of the maxilHpede had 6 plumose setse ; but instances of 

 4 and 8 were obsei"ved. 



This form has long blanched pleopods (fig. 1b). The abdomen consists 

 of six segments and the telson. The telson retains the narrow form of the 

 I. Zoea, but it has an exti-a little hair on the inside of the fork. Some- 

 times one, sometimes the other, tooth on the outside of the prong appears 

 the bigger. 



III. Zoea cast into the Megalops, 



The Zoea period therefore appears to consist of three stages. 



Megalops. Fig 2. 



This stage resembles in pigmentation the Zoea. The red colour in the 

 drawing is not quite the right shade. The pereiopods are red in parts. The 

 abdomen also has red pigment, although none had apparently been present 

 in the specimen di-awn. The eyes show a white exterior, but some purple 

 pigment is present within. 



The Megalops has a trident ate frontal region. A smooth doi^\l spine 

 rises from the hind half of the cai"apace. Just behind the eyes there is a 

 pair of lateral hooks, and between them in the middle doi^sal Hne there is 

 a median ridge, seen in side view in nv., fis:. 83. 



