fctES AND SCALES OP PISHES. 379 



ciila, and entangling them in it. Many, however, continue 

 their motion as before. 



Whether these bodies really turn upon their axes, or whe- 

 ther they have the property of producing a rapid renewal and 

 cessation of reflection of the rays of light, from their surfaces, 

 so as to produce only the appearance of rotation, I cannot po- 

 sitively determine. In the larger spicula of the choroid of the 

 herring, I have certainly, sometimes, been able to trace the 

 opaque outline of an individual spiculum, after it had ceased 

 its twinkling reflection ; but, in general, the appearance of ro- 

 tation seems so distinct, as almost to preclude the supposition 

 of its not really taking place ; and these bodies are not so mi- 

 nute as to admit of much optical deception ; for in those from 

 some fishes, the herring in particular, the reflection, and ap- 

 parent motion, are quite evident, in the sunshine, to the naked 

 eye. 



The spicula of the eye of the herring are jointed, being ge- 

 nerally thus divided into three distinct portions, of which that 

 which forms the centre is much larger than the two others. 

 In common day-light, the entire spiculum is silvery ; but if it 

 be observed in the sunshine, it will be found to reflect different 

 rays, from the different jointed portions ; the end-joints being 

 generally of a light straw colour, while the central one is steel- 

 blue, like the main-spring of a watch, or of a red or light rose 

 colour, sometimes silvery, green, or purple ; but never of the 

 same colour as the extremities of the spiculum. The colours 

 of the different joints do not shade into each other, but ter- 

 minate abruptly by a well-defined line. 



To account for the motion of these spicula is difficult. 

 There seems no reason to suppose it to depend, either on elec- 

 trical or galvanic influence. The motion of each spiculum is 

 proper to itself, nothing like attraction, or repulsion, subsisting 



between 



