S/6 ANATOMY AND DEVELOPMENT 



The ambulatory appendages, with the exception of the fourth 

 and fifth pairs in both sexes, and the last pair (seventeenth) in 

 the male, all resemble each other fairly closely. A typical ap- 

 pendage (figs. 2 and 3) will first be described, and the small 

 variations found in the appendages just mentioned will then 

 be pointed out. Each consists of two main divisions, a larger 

 proximal portion, the leg, and a narrow distal claw-bearing 

 portion, the foot. 



The leg has the form of a truncated cone, the broad end of 

 which is attached to the ventro-lateral body-wall, of which it 

 appears to be, and is, a prolongation. It is marked by a number 

 of rings of primary papillae, placed transversely to the long axis 

 of the leg, the dorsal of which contain a green and the ventral a 

 brown pigment. These rings of papillae, at the attachment of 

 the leg, gradually change their direction and merge into the 

 body rings. At the narrow end of the cone there are three 

 ventrally placed pads, in which the brown pigment is dark, and 

 which are covered by a number of spines precisely resembling 

 the spines of the primary papillae. These spinous pads are con- 

 tinued dorsally, each into a ring of papillae. 



The papillae of the ventral row next the proximal of these 

 spinous pads are intermediate in character between the primary 

 papillae and the spinous pads. Each of these papillae is larger 

 than a normal papilla, and bears several spines (fig. 2). This 

 character of the papilla of this row is even more marked in 

 some of the anterior legs than in the one figured ; it seems 

 probable that the pads have been formed by the coalescence of 

 several rows of papillae on the ventral surface of the legs. On 

 the outer and inner sides of these pads the spines are absent, 

 and secondary papillae only are present. 



In the centre of the basal part of the ventral surface of the 

 foot there are present a group of larger papillae, which are of a 

 slightly paler colour than the others. They are arranged so as 

 to form a groove, directed transversely to the long axis of the 

 body, and separated at its internal extremity by a median papilla 

 from a deep pit which is placed at the point of junction of the 

 body and leg. The whole structure has the appearance, when 

 viewed with the naked eye, of a transverse slit placed at the base 

 of the leg. The segmental organs open by the deep pit placed 



