BY E. J. GODDARD. 731 



There is every reason to believe that this same constitution 

 holds in the case of GeohdeUa. Cascles, in his excellent work, 

 has laid down the following generalisation in regard to the 

 metameric significance of sensill^, namely, that the sensory ring 

 occupies the middle of the somite. 



In examining the present species for sensillse, I found, under 

 contraction due to the action of the killing fluid(alcohon, that 

 there were strongly marked divisions regularly arranged, on the 

 ventral surface. In examining these carefully, I found that each 

 division consisted of five(5) annuli, and, by this means, I used a 

 count of the annuli to see how these divisions would correspond 

 with those into which the body would fall by using Whitman's 

 or Castle's method, respectively, in conjunction with the assist- 

 ance rendered by an examination of the markedly sensilliferous 

 species, G, Whitmani. The result was that they corresponded 

 exactly with that laid down in the table given above. 



It would certainly seem to denote that, in this genus, the 

 sensillse mark off the first annulus of a somite. It is quite pos- 

 sible that there is no constancy in regard to the position occupied 

 in a somite by the sensilliferous annuli in leeches in general, but 

 it may be always the same in the same genus, as in Glossiphoiiia, 

 for instance, where, no doubt, the sensilliferous annulus is the 

 middle one of the triannulate somite. I have pointed out in a 

 previous paper, in connection with the description of the genus 

 Semilageneta, the impossibility of allotting the annuli in the 

 manner suggested by Castle, for that genus. 



That variation takes place among the sensillse can be seen in 

 Glossiphonia heteroclita, in which the eyes are usually situated on 

 annuli 5, 7, 8, and at other times on annuli 6, 7, 8; and the eyes 

 are really modified sensillse, and have the same metameric 

 significance. 



