A STUDY IN MORPHOLOGY. 87 



another at the base of the telson ; and the dorsal surfaces of the fifth, fourth, and 

 sometimes the third abdominal somites are irregularly marked, near their posterior 

 edges, by patches of the same colour. The anal pigment-spots are of a dirty red 

 colour. 



The Lucifer stage. 



The specimen from which fig. 61 was drawn was a little more than half an inch long, 

 or about half as large as an adult specimen. It differs in several particulars, besides 

 size, from an adult male, but in all respects except size and the presence of reproduc- 

 tive organs it is exactly like a mature female. Its appendages are like those which 

 are shown in figs. 63 to 70, although these were drawn from an adult female specimen. 



The adult structure of our American species has been described by FAXON (' Studies 

 from the Biological Laboratory of the Johns Hopkins University,' vol. i., part iii.) ; 

 but as he had only a single male specimen, which had been preserved in alcohol, his 

 account was necessarily somewhat incomplete. 



The first antenna (Plate 7, fig. 61, and Plate 8, fig. 66, A) is about as long as the 

 carapace and neck, and it is divided into two nearly equal portions, the base (fig. 66, i) 

 and the flagellum (fig. 66, 2). The base is divided into three joints, the first about as 

 long or a little longer than the eye, the second much shorter, and the third still 

 shorter. The large ear occupies the centre of the proximal end of the first joint. On 

 the outer end of the first joint and on the second there is a row of six short, equal, 

 plumose hairs, three on each joint. The flagellum is made up of ten joints ; the first 

 and second are thicker than the others, and the first carries two and the second three 

 sensory hairs. The terminal joint of the flagellum is much longer than the other, and 

 carries a few very short hairs at its tip. 



The second antenna (figs. 61 and 66, An] is, in the fully-grown specimen, almost 

 twice as long as the first, and nearly or quite as long as the body. It consists of a 

 very short basal joint (fig. 66, a), which carries the scale (ex) and the flagellum (en). 

 The scale is somewhat longer than the eye, flat and narrow, and its inner edge carries 

 nine and its tip three long, slender, plumose haii-s, which are about half as long as the 

 scale itself. The flagellum tapers gradually from the base to the tip, and is made up 

 of twenty-four joints, each of which carries a pair of very short hairs. The joints at 

 the tip of the flagellum are a little longer than those at the base. The living animal 

 usually carries these appendages extended before it, and diverging a little at their tips. 

 It occasionally throws them back along the sides of the body, but only for an instant 

 at a time. 



The eye-stalk tapers gradually from the base to the tip, and there is no abrupt 

 distinction between the stalk and the eye proper, as there appears to be in other 

 species. The length of the eye, with its stalk, is a little less than that of the true 

 carapace. 



The neck makes a little more than three-fifths of the total length of the carapace, 



