BY E. J. GODDARD. 61 



was the same as tliat entering into the somitic constitution, and 

 their presence seemed to denote a more intimate connection of the 

 annuli composing each group, with each other than with the 

 aunuli of another group. 



On this reasonable assumption it was found that the sensory 

 annulus was denoted by the third annulus of tlie somite. It has 

 been definitely proved that the sensory annulus occupies the 

 same position among two of the otlier three tetrannul ate forms — 

 Pontohdella and Ozohranchti^ hranchiatiis — so that we can safely 

 conclude that the somite-limits are thus definitely shown by the 

 assistance given by the furrows mentioned above, and that the 

 sensory annulus is the third ring of the adult somite. 



Reasons will be advanced later to show that all the tetrannulate 

 leeches are similarly constituted in this respect. 



Geobdella tristriata. — In examining a single specimen of this 

 newly ])roposed species, gaps somewhat similar to those observed in 

 the case oi PhiUHmott ^j?t/i</e?is were noted, and these are evidently 

 due to a buckling of the bodj^ as the resultant of the effect of 

 the killing fluid. These I proved, in the case of Fhilcumon, to 

 mark oS" the somite-limits, so that I have reasonabl}' concluded 

 that the same holds in this case. Geobdella is a pentannulate 

 genus. In the two Australian species there are well developed 

 papillfe, but I was unable to detect any such structures in 

 the killed specimen of G. tristriata. However, inasmuch as the 

 eyes hi,ve the same disposition, and the number of annuli is the 

 same in all species, I have legitimately made use of the disposition 

 of the papillse as denoted in the other species, in mfipping out the 

 position of the sensory annulus in G. tristriata. In the manner 

 denoted above, the greater p.irt of the body is divided up 

 into groups consisting of five annuli; and, by taking into account 

 the position of tlie jiapillae in the other species and the position of 

 any of the above-mentioned gaps, I found that the sensory annulus 

 was denoted by the first annulus of the pentannulate somite. 

 ^ It is interesting to note that in Philcemon and Geobdella, which 

 anatomically are closely allied, the somite-limits were denoted in 

 the peculiar manner indicated above. The fact that this occurs 



