MB. F. E. BEDDABD ON AN ANNELID 



[Feb. 5, 



82 



which it will be seen that a semicircular depression with_the con- 

 cav'tv directed forwards is the external m anilestation of the organ, 

 of which the mass of cells lie behind. 



In a specimen in which the prostomial organ is lateral m position 

 (text-fig! 8,B), an external depression is to be seen with equal clear- 



Text-fig. 8. 



Bothrioneuroii iris. 

 Fig. A. Prostomium from below. Fig. B. Ditto from above. 

 8, sense-organ symmetrically placed in A, asymmetrically in B. 



Text-fig. 9. 



Sotkrioneuron iris. 

 Longitudinal section through the prostomium. 

 S, sense-organ ; B, supra-cesophageal ganglion. 



ness, but naturally in profile. In a longitudinal section (text-fig. 9) 

 of a specimen in which the sense-organ happens to be median and 

 quite anterior in position, the following appearances are observable : 

 the supposed sense-organ consists of a mass of cells which are rather 

 deeper than are those of the surrounding epidermis ; this is especially 



