258 BULLETIN OF THE 



an outer lobe (5) ; the outer lobe bears the palpus (c). All the parts which 

 compose the first maxilla are furnished with plumose setse. The second pair 

 of maxillae (PL II. Fig. 11) consist of four lobes of about equal size, a narrower 

 lobe, and a scaphognathite (a) ; all of these lobes are fringed with plumose setse 

 on their margins. 



The two pairs of swimming-feet (first and second maxillipeds) (PL II. Pier, i) 

 are very similar to each other in form. The outer branch is two-jointed, the 

 inner branch four-jointed. The third pair of maxillipeds (PI. II. Figs, l, 12) 

 are rudimentary, sac-like structures, which can hardly as yet be of much func- 

 tional value. They are, however, developed so far as to project beyond the 

 border of the carapace. The inner branch (Fig. 12 a) is much longer than the 

 outer (b). The latter is tipped with long setae. Through the transparent sac- 

 like integument the segments of the outer maxilliped of the next stage may be 

 indistinctly seen. 



The five pairs of ambulatory limbs of the future crab are doubled up under 

 the carapace (PI. II. Fig. 1). By removing them from the body of the zoea 

 their whole form is seen as represented in PL II. Fig. 13. Through the thin 

 investing membrane the segmentation of the limbs is quite distinctly seen as it 

 exists in the following stage after the tegument has been thrown off. Even the 

 hooks on the last segment of the second, third, and fourth pairs are visible (&'). 

 At the base of the thoracic appendages the gills (six pairs) have already attained 

 a considerable size (Figs. 1, 13/). 



The abdomen is composed of six segments. The telson (PL II. Fig. 5) is pro- 

 duced on either side into a strong tooth ; the posterior margin is very convex, 

 scalloped, and ornamented with twelve beautiful, feather-like setae. In speci- 

 mens about to moult the telson is seen to contain the sixth abdominal segment 

 (6) with its appendages (c, cT), as well as the telson (a) of the crab. There is a 

 pair of simple unsegmented appendages on the second, third, fourth, and fifth 

 segments of the abdomen (PL II. Figs. 1, 14). 



The stomach shows through the transparent carapace just back of the base 

 of the rostrum. On either side are four lobes of the liver, two directed for- 

 ward, two backward. The intestine is straight and simple, and ends in the 

 fore part of the telson below. The heart lies under the centre of the carapace ; 

 from its anterior angle the median artery can be traced nearly to the end of the 

 rostrum ; the sternal artery reaches the lower floor of the thorax near the roots 

 of the third pair of maxillipeds, passing through the great thoracic nerve-mass ; 

 here it forks, one branch proceeding forward, giving off in its course lateral 

 branches to the anterior appendages, the other backward to the abdomen. 



The nervous system departs widely from its primitive condition even in this 

 immature stage. The thoracic ganglia are consolidated into an enormous mass 

 which sends nerves to the thoracic appendages. From this thoracic nerve-mass 

 two parallel nerve-cords extend through the abdomen, binding together the 

 ganglia, which lie one in each abdominal segment. 



The integument is nearly colorless, with some spots of vermilion pigment 

 on the basal segments of the first and second pairs of maxillipeds, on the tel- 



