500 /• PERCY MOORE. [Vol. X. 



prominent bellying of the free hypodermis when the longitu- 

 dinal muscles shorten. 



Of the body somites, the fifth, sixth, and seventh are the 

 sexual; the first four and the eighth nephridial. The external 

 opening of the anterior pair of nephridia is readily seen on the 

 mid-dorsal line of the major annulus of the third post-cephalic 

 somite (Fig. i, m), and the paired pores of the posterior pair 

 in a dorso-lateral position between the eight and ninth somites. 

 Of the three enlarged sexual somites the sixth and seventh are 

 rendered opaque by the great development of aggregations of 

 unicellular glands constituting a clitellum. On the fifth a 

 slight swelling on the ventral surface of the major annulus in- 

 dicates the position of the external spermathecal opening, and 

 a more prominent enlargement of the corresponding region of 

 the succeeding segment the mouth of the copulatory bursa 

 (muscular atrium) (Fig. i, z)- The external ovipores are rela- 

 tively minute apertures ventrally located on each side of the 

 seventh somite (Fig. 1,9), between the major and minor annuli. 

 The anus opens on a small lobate papilla on the dorsum of the 

 tenth somite (Figs, i and 5, a). 



Bundles of ductules arising from the huge mucous glands 

 which occupy the lateral regions of the nine anterior seg- 

 ments, pierce the hypodermis, and open on the surface of the 

 body in the dorsal and ventral quadrants of the major annuli. 

 The sucker-bearing somites are much crowded ; and bi-annula- 

 tion is only obscurely indicated. The acetabulum itself is 

 a complex muscular ring or disk, having a slight posterior 

 concavity. Its centre lies in the same axis as the body somites, 

 so that in a position of rest the body of this species is strongly 

 arched, instead of resting extended along the surface to which 

 it is attached, as is the case with the species having depressed 

 forms and ventrally directed suckers, which live on the broad 

 surfaces of the chelae and carapace of crayfish. 



Body walls. — The body walls are made up of the usual suc- 

 cession of an epidermis with its continuous cuticular covering, 

 an external layer of circular muscle fibres, and an internal more 

 powerful layer of longitudinal muscle fibres. The delicate cuti- 

 cle is quite continuous, and follows the epidermal cells by which 



