340 AUSTRALIAN HIRUDINEA, I., 



first but the middle annulus of a somite as far as the species of 

 Glossiphonia are concerned. That this is not the case in the 

 genus here described can be seen by glancing at fig. 13. 



The first somite is uniannulate, and has on its dorsal surface 

 six papillae. The second somite is biannulate, and has six papillae 

 on the first annulus. The two papillae nearest the mid-line are 

 much larger than the lateral pairs. The remaining somites are 

 triannulate. In the third and fourth somites the sense papillae 

 are similar to those of the second somite. The papillae are 

 similarly arranged on somites v.-xi. inclusive, but are all of the 

 same size and much smaller than on the preceding somites. 

 Behind the eleventh somite the papillae disappear; and the 

 somites are distinctly marked off by definite sulci, producing a 

 lobed margin, as can be seen in figs. 11 -12. Nine such somites can 

 be made out behind the eleventh in dorsal view. The sulci do 

 not reach the mid-line, and along that region is a well marked 

 ridge. The nineteenth somite is wedged in between the 

 eighteenth and twentieth in a peculiar fashion. 



The total number of annuli is sixty-eight, sixty lying behind 

 the posterior margin of the oral sucker. The annuli of somites 

 eleven to eighteen inclusive are much larger than those of the 

 remaining portion of the body, and increase gradually -in size as 

 they pass backwards from the eleventh somite. The annuli of 

 the first eleven somites are very distinctly marked off from one 

 another, the division in the case of the others being denoted by 

 a fine line. The arrangement of the papillae indicates that the 

 somites in the greater part of the body are triannulate. This is 

 corroborated by the arrangement of the ganglia in the ventral 

 nerve-cord. In making an incision in the organism preparatory 

 to imbedding in paraffin, I exposed portion of the nerve-cord and 

 found that three ganglia thus seen each supplied three aonuli. 



If, as Castle found in species of Glossiphonia, the sense papillae 

 occurred not on the first annulus of a somite but on the middle 

 one, it would be found that the first somite would be uniannulate, 

 the second uniannulate, and the third triannulate; or the second 

 biannulate, and the third biannulate, the remaining somites being 



