some Marine Invertebrata. 33 



Dr. Coldstream seems not to have known of two memoirs 

 which appeared in Germany, about the same time, and which we 

 have reserved for the close of this history, on account of their 

 peculiar interest. 



The first of these works is that of M. Ehrenberg*, and it is in- 

 contestably the most complete which has been published on this 

 subject. To all the facts made known by his predecessors, the 

 author adds the result of his own'^ investigations in many seas. 

 At Alexandria he established beyond doubt the fact that the 

 Spongodium vermiculare, as also other Algae regarded as phos- 

 phorescent, owe this appearance only to the luminous animal- 

 cules adhering to their surface. He describes a new species of 

 Polynoe (P. fulgurans) found by him in the Baltic, that appa- 

 rently plays an important part in the phosphorescence of that 

 sea, which also owes its luminous properties to different infu- 

 soria. At Christiana and at Heligoland, Ehrenberg observed this 

 phEenomenou in many species of Meduste; at the last locality 

 he met with the Noctiluca miliaris, which he calls Mammmia. 

 Ehrenberg describes also the very remarkable mode of phospho- 

 rescence which appeared in a Nereid, the Photocharis cirrhigera. 

 In that Annelid, the light proceeds from two thick and fleshy 

 cirri belonging to the dorsal branch of the feet. The author 

 observed sparks, at first isolated, invade the cirri by degrees, 

 until they became luminous in their whole extent ; then the 

 phosphorescence spread through the whole back, until the animal 

 looked like a thread of burning sulphur. The mucus secreted 

 by the Photocharis left on the fingers a luminous trace. In the 

 Polynoe fulgurans, Ehrenberg regards two large rough bodies, 

 resembling ovaries, as charged with producing the light. In the 

 Cydippe pileus and in the Oceania pileata, he found that the 

 light starts from the centre, that is, in the neighbourhood of the 

 reproducing organs. In the Oceania hemispihcerica, a species 

 whose diameter is more than an inch, Ehrenberg saw the sparks 

 from a chaplet around the border ; these correspond to the large 

 cirri or to the organs alternating with them. 



Ehrenberg sums up in the following manner the important 

 results of his labours : — 



1st. The phosphorescence of the sea appears to be owing 

 solely to organized beings. 



3nd. A very great number of organic and inorganic bodies 

 shine in the water and out of the water in different ways. 



3rd. There is also a light from organized bodies, which is 

 probably owing to vital action. 



4th. The active organic light shows itself frequently under 

 the form of a simple flash, repeated from time to time, sponta- 

 * hoc. cit. 



