Sfracfiive of o u Anstraliaii Land LeecJi. 215 



Whitman determines the segments by the position of the 

 segmental papilUe, which he states are present on the first ring 

 of every somite. Oka is unable to fix the somites by this means 

 and points out that if these papilU>3 were as distinct in all species 

 as those described by Whitman it would not be difficult to make 

 out the somites and the number of annuli contained in each. I 

 have found the same difficulty in determining the somites by the 

 papilltB. In many of the specimens it is quite impossible to detect 

 any such sensory organs except by means of sections ; other 

 leeches, however, which resemble the former in every respect, 

 possess on every fourth ring twelve papilla?. These are definitely 

 arranged as shown in Fig. 3, and occur in constant relation to 

 the external markings of the leech. Along the mid-dorsal sur- 

 face from the anterior to the posterior end of the body is a 

 narrow light brown band, on each side of which is a broad and 

 darker area extending to the lateral-ventral margin. Immedi- 

 ately on either side of the mid-dorsal band, except at the 

 extremities, is a series of pale grass green patches of pigment. 

 Each patch extends through three annuli, and at its anterior 

 and posterior end is a papilla, that is, every fourth annulus, and 

 only every fourth, possesses segmental papilh\?. Tlie green patch 

 is outlined in very dark brown, almost black, colouring matter. 

 On the lateral edge, where the dark dorsal area meets the pale 

 ventral surface, another papilla occurs, and midway between this 

 and the dorsal papilla is a third, so that on the dorsal surface 

 there are six segmental papilla? — that is, three on each side of 

 the middle line. 



The under surface of the leech is of a uniform light brown 

 colour, and on the ventral surface of each papilla-bearing annulus 

 there are, as on the dorsal, six papiihe. 



As is seen in Fig. 1 there are four annuli between the male 

 and female genital openings. By means of sections I find that 

 the nephridiopores occur on every fourth ring, and there are also 

 four annuli between each of the sixteen nerve ganglia in the 

 region of the body. Therefore, it may be concluded that there 

 are four annuli to each unabbreviated somite. 



Pontobdella among the Rhynchobdelhe and Orobddla whit- 

 mani of the Arhynchobdellaj are the only other leeches as yet 

 described which agree with Philjemon in this respect. 



