A STUDY IN MORPHOLOGY. 107 



The three pairs of pleopods are alike in structure, and each consists of two joints 

 about equal in length (fig. 89). The outer half of the terminal joint is toothed and 

 carries six pairs of long slender non-plumose hairs, so arranged as to form a paddle. 



The rostrum (fig. 85) is long and curved, and it has a single secondary spine in its 

 upper surface. A pair of very small spines have also appeared at its base. 



This specimen had nearly completed its moult into the stage shown in fig. 90 on 

 the last day of my stay at the seashore five days after fig. 85 was drawn. 



Fig. 90 was drawn from another specimen, -^ Q inch long, which was captured at 

 the surface on September 25th. 



The eye-stalks are long and very movable, the flagelluui of the second antenna is 

 considerably longer than the body, the five pairs of thoracic limbs have developed gills, 

 and the fourth and fifth pleopods have appeared ; but in other respects the structure is 

 nearly as it was in the preceding stage. The endopodites of the maxillipeds are 

 pointed, but those of the three pereiopods end in rudimentary chela?. The endo- 

 podite of the third pereiopod is much longer and thicker than the others, and its tip 

 reaches nearly to the rostrum. 



The buds for the first three pairs of pleopods are long, obscurely jointed, and they 

 meet each other on the median line. There are as yet no traces of the fourth and 

 fifth pairs. The spines on the abdominal somites are long and sharp. Those on the 

 first three somites point outwards and forwards, those on the fourth point almost 

 directly outwards, and those on the fifth outwards and backwards. The sixth abdo- 

 minal somite has lengthened, and is now about as long as those of the others. The 

 telson is short and shield-shaped, with two pairs of long and one pair of very short 

 spines, and the swimmerets are perfectly formed and fringed with long plumose 

 swimming hairs. 



The exopodite is long, narrow, with a smooth outer edge which ends in a tooth, and 

 a rounded point. It carries fifteen hairs : ten on the inner edge, two on the tip, and 

 three between the tip and the tooth. The endopodite is nearly as long and wide as 

 the exopodite, and it carries nineteen hairs : two at the end, eight on the outer, and 

 nine on the inner edge. 



The ocellus is still present, and the pigment-spots have nearly the same arrangement 

 as before, but some of them are now yellow or green instead of red. 



The eye-stalk is about as it was before, and the ocellus is still present and double. 

 As regards the more minute structure of the appendages the first antennae are now 

 about as long as the carapace, and most of the increased length is in the flagellum, 

 which now consists of seven joints. The secondary flagellum is still quite short. The 

 shaft of the antenna is three-jointed, as before, but the basal joint is much lengthened, 

 and now makes more than hah the total length. The auditory organ at its base is now- 

 very conspicuous, and the inner edge of the shaft carries eleven hairs instead of six ; 

 five of these are on the basal joint, three on the second joint, and three on the third. 



The scale of the second antenna has lengthened and is now more than half as long as 



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