Phosphorescent Animals. 71 



pass through fine gauze ; yet many were distinctly 

 visible by the naked eye. The water, when placed 

 in a tumbler and agitated, gave out sparks, but a 

 small portion in a watch-glass scarcely ever was 

 luminous. Ehrenberg states that these particles all 

 retain a certain degree of irritability. My observa- 

 tions, some of which were made directly after taking 

 up the water, gave a different result. I may also 

 mention that, having used the net during one night, 

 I allowed it to become partially dry, and having 

 occasion twelve hours afterwards to employ it again, 

 I found the whole surface sparkled as brightly as 

 when first taken out of the water. It does not 

 appear probable, in this case, that the particles could 

 have remained* so long alive. On one occasion, 

 having kept a jelly-fish of the genus Diancea till it 

 was dead, the water in which it was placed became 

 luminous." 



Since Darwin made his famous trip scores of ani- 

 mals have been added to the list of those which emit 

 light, yet the true secret of the illumination has not 

 yet been determined. 



