158 Prof. J. Wood-Mason's Morphological Notes 



at its distal extremity into at least four brandies, Avliicli 

 traverse the glandular tissue and are inserted into the 

 inner surface of the thin, smooth, and delicate epithelial 

 membrane constituting the wall of the protruded bladders. 

 Whether the bottom of the hilus-like depression seen at 

 the extremity of each of them is j^rolonged into a tube 

 opening into, or ending blindly in, the body-cavity, I have 

 not yet been able to make out, but when the bladders are 

 drawn in their external surfaces become the walls of glan- 

 dular pouches, each o])ening to the exterior by a pore, which 

 is defended by a chitinous operculum fringed with seta3 on 

 its free margin. 



Ficr. 3. 



Fig. 3. Macliilis marlfinia; sternum with appendages of 2nd abdominal 

 somite ; st, sternum ; p, the coalesced basal joints of the 

 right member ; o, the fringed opercula covering the external 

 apertures of glandular pouches supposed to be homologous with 

 the nephridia, renal pouches, or segmental organs of worms ; 

 a, the exopodite, or outer branch of the member. This sternum 

 only differs from a thoracic sternum in the absence of ambulatory 

 legs (endopodites), and in the presence of glandular pouches. 



The second to the fifth somites are each provided with 

 four such })ouches, viz., two opening close together near 

 and internally to each exopodite ; but the sixth and seventh, 

 as also the first, which has lost its exo[)odites, have only a 

 single pair. 



