BY WILLIAM A. IIASWELL, M.A. B.SC. 255 



When certaia species of Pohjno'c are irritated in the dark a 

 flasli of phosphorescent light will be seen to run along the 

 scales, each being illuminated with a vividness which makes it 

 shine out like a shield of light, a dark spot in the centre repre- 

 senting the surface of attachment where the light-producing 

 tissue would seem to be absent. The irritation communicates 

 itself from segment to segment, and, if the stimulation be 

 sufficiently powerful, flashes of light may run along the whol 

 series, one or more of the scales then becoming detached and 

 being left behind still glowing with phosphorescent light. The 

 species characterised by the phosphorescence of their scales are 

 species also distinguished by the celerity of their movements and 

 also by the readiness with which their scales are parted with 

 when the animal is attacked ; and it may be that the phos- 

 phorescence has a protective effect, the phosphorescent scales 

 thrown off by the annelide distracting the attention of an 

 assailant and enabling the former to make good its escape. 



That the scales act, like the dorsal cirri, as organs of some 

 special sense seems probable from their abundant innervation, as 

 well as from the presence in many instances of fimbriae and other 

 appendages, some of which appear to be the end-organs of the 

 nerve-branches. These appendages, the form of which varies 

 greatly, are processes of the upper wall of the scale, and probably 

 consist of the cuticular, subcuticular, and fibrous layers of the 

 latter ; the subcuticular layer is in most instances, however, 

 difficult to make out, owing to the thickness of the cuticle, but 

 in one species of Folynoc, I find that certain vesicular processes 

 which present a very delicate cuticle shew distinctly below it 

 the layer of polygonal cells, and in the interior a series of fibres 

 which radiate from the base of the vesicle to its outer wall, and 

 many represent the fibrous layer of the scale, or may be of 

 nervous nature. 



In Aplirodifa and Uermione the scales have been observed by 

 Williams and Quatrefages to perform an important mechanical 



