434 " THETIS " SCIENTIFIC RESULTS. 



not to say that the other does not exist ; it probably does, but 

 owing to the poor condition of my material was not found. 



3. Nephridium. 



Of this organ I can only say that its external appearance is 

 similar to that of M. aruanus. The glandular lamellae and reti- 

 culation of blood vessels were completely destroyed. One or two 

 pores were found occupying a position similar to that of the pores 

 of the nephridial gland in the last species, but no trace of the 

 gland was found. There is no ureter^ and the reno-fallial orifice 

 is large and easily seen. 



4. Vascular system. 

 (PI. xxxix., fig. 6.) 



The most careful attempts at injection met with complete 

 failure, as the walls of the vessels were too soft to retain the 

 fluid. This section is, therefore, confined to the pericardium, 

 heart and aorta-cephalica. 



The pericardium is disproportionately smaller than that of M. 

 aruanus, and is almost filled by the contained organs, namely, 

 heart, aortse and posterior oesophagus. 



The heart almost exactly resembles that of the other species, 

 and is hardly, if at all, smaller. 



The aortce are fused at their origin, as in the other species ; 

 only that short piece of the aorta-visceralis, lying within the 

 pericardium, was seen. 



The aorta-cephalica {ao. ce.) passes forward in the same course 

 as in the species just discussed, but the right branch is quite 

 insignificant when compared with this branch in that species. 

 At the anterior end of the body cavity the artery lies in the 

 middle line ; just posterior to the nerve-ring it gives off a branch 

 which passes down into the tissues of the foot ; it then passes 

 through the nerve-rincc, in the same course as the oesophagus, 

 and immediately divides into three. Two of these pass down 

 into the tissues to supply the propodium, the third branch 

 bends back, and accompanies the cesophagus along the pz'oboscis 

 sac, and into the proboscis. 



5. Nervous SystExM. 

 (PL xl, figs. 2 and 3.) 



This system was only dissected out with difficulty. The trouble 

 arose from two causes, one was that the material had been in weak 

 alcohol for nearly thirteen years ; but more serious than this was 

 the fact that the anterior end of the body cavity was, as in the 



