A STUDY IN MORPHOLOGY. 81 



concerned, with the Elaphocaris stage of Scrgestcs, although the most conspicuous 

 features of the Elaphocaris larva, the long compound spines, are not present in Lucifer. 

 It is now about ytHfo inch long, and it is shown in a dorsal view in Plate 5, fig. 44, 

 and, more highly magnified, from below in Plate 4, fig. 43. In a side view (fig. 45) 

 it still agrees pretty^ closely with fig. 35 ; its body is carried in the same attitude, 

 and the antennae are still the chief organs of locomotion. The fully-developed 

 appendages are, as before, the first and second antennae, the mandibles, two pairs of 

 maxillae, and the first and second pairs of maxillipeds, but the third pair of maxillipeds, 

 four pairs of thoracic appendages, and the swimmerets or appendages of the sixth 

 abdominal somite are now present as rudimentary buds. 



The compound eye (figs. 43 and 45, E] is now well advanced in development, although 

 there is as yet no trace of a stalk, and the cornea is simply a modified portion of the 

 integument of the carapace. 



The carapace is longer, narrower, and more rectangular in a dorsal view than it was 

 at the last stage, and it makes only about one-third of the total length of the body of 

 the larva. Its pigment-spots are very large, dendritic, and conspicuous, but their 

 colour has changed from black to dark reddish-brown. 



The anterior lobes of the stomach (fig. 44, s) have lengthened and approached each 

 other on the median line, and they now reach forwards nearly to the optic ganglia. 



The appendages which were present during the Protozoea stage have essentially 

 the same structure now, and the differences are very slight. The number of cutting 

 hairs on the basal joints of the first maxilla (fig. 46) has increased ; the hairs on 

 its endopodite are plumose, and one of those carried by the scaphognathite is much 

 longer than the other two. This is the case also with the second maxilla (fig. 47), 

 and the hairs along its inner edge have become almost as long and slender as those at 

 its tip. The first maxilliped (fig. 48) is almost exactly like that of the Protozoea; 

 but the second (fig. 49) is much more developed, and the hairs on its exopodite are 

 plumose. 



The hind body is now divided into its full number of segments ; that of the third 

 pair of maxillipeds (Mp. 3) ; the first, second, third, and fourth thoracic somites (T 1, 

 T 2, T3, and 7*4); and the six abdominal somites, but the telson (T) is not yet com- 

 pletely distinct from the last abdominal somite. The thoracic somites are shortened 

 and crowded together, and each of them carries a pair of bilobed buds, the rudi- 

 mentary thoracic appendages. These buds are crowded together in a double row on 

 the median line of the ventral surface of the body, and outside them is a pair of 

 much larger buds (figs. 43 and 45, Mp. 3), bilobed also, but pointing backwards ; the 

 rudimentary third pair of maxillipeds. 



The future history of the larva seems to show conclusively that the inner set of 

 buds are, as indicated in fig. 43, the first four pairs of thoracic limbs or pereiopods. 

 The side view (Plate 5, fig. 45) shows that there is no other pair in front of or 



MDCCCLXXX1I. M 



