52 MEMOIR III. 



unprovided with a microscope, or incompetent to tlie task 

 of developing the structure of such small olyects as are 

 thus procured, they can be preserved in a closely corked 

 phial of spirits unchanged for any length of time, with the 

 exception of such as /ee? soft, gelatinous and yielding, which 

 being species of Medusae, cannot be kept from dissolution 

 by any of the means hitherto tried, and if mixed with the 

 others might tend to cause the corruption of the whole ; 

 these therefore, should be carefully separated and rejected, 

 or what would be still better, every kind might have a phial 

 to itself. When the luminous animals are observed to be 

 remarkably numerous, they may also be conveniently ob- 

 tained by drawing up a bucket-full of the water, from 

 which they may be separated by means of a small wire 

 hoop or open spoon covered with muslin. 



Genus 1. 



Nocticida, or Luminous Shrimp. 



The animal which forms the type of this Genus, was 

 first discovered by Sir Joseph Banks, in the passage be- 

 tween Madeira and Brazil. Observing that the sea was 

 particularly luminous, he had some of the water drawn 

 up in a bucket, and found that the sparkling appearance 

 was owing to the present animal, which he therefore 

 named Cancer fulgens. (Macartney Phil. Trans. 1810.) 

 The drawing which Sir Joseph caused to be made of 

 it, and published in the paper above referred to (PI. 

 XIV. f. 1 and 2) and copied PL 5 f . 2 although perhaps 

 not remarkably exact, shews that it approximates the 

 Opossum Shrimp (Mysis) in figure, and in the number and 

 structure of its members. Having had an opportunity of 

 taking numerous individuals of the Luminous Shrimp, in 

 my homeward passage from the Mauritius, I have been 

 enabled to figure it with more care, PI. 5 f . 1 : Making 

 due allowance for drawings made at sea of suchminute 



