Luminous Animals. 249 



much interest in pursuing a track which has been laid down by 

 their predecessors, unless perhaps for the purpose of controvert- 

 ing or disputing the principles or facts on which it has been 

 grounded, I thought it right to make use of such further oppor- 

 tunities as might occur towards the accumulation of new matter 

 on this subject, and towards confirming the opinions stated in the 

 paper to which I have alluded. A voyage to the Shetland and 

 Orkney Islands afforded these opportunities; and the result has 

 been to confirm the former views, by a series of observations 

 carried on daily for many weeks. By these a large addition has 

 been made to the list of luminous animals which was given in 

 that essay ; and it has been, in particular, proved, that the sea 

 is very often crowded with worms and insects, often nearly 

 invisible ; and that the luminous property of the water, not only 

 bears a relation to the existence and numbers of these at any 

 time, but may almost always be traced to the individuals by 

 which it is caused. 



Those who are acquainted with this obscure and much 

 neglected department of Natural History, will not be sur- 

 prised to hear that I cannot at present give names to the 

 numerous individuals which I examined for this purpose. 

 Among them are many objects, of which, not only the names 

 are doubtful, but the very genera, and even the analogies, ob- 

 scure or uncertain. Many are absolutely unknown, and con- 

 stitute new species which it will be my business to describe 

 hereafter, when all the requisite comparisons have been made. 

 For the present purpose, it is as unnecessary, as it would be im- 

 possible, to enter into details of so extensive a nature as would 

 be required for assigning the names of the various animals in 

 which I have now observed the property of emitting light, in addi- 

 tion to that list which was given in the essay to which I have 

 here referred. 



It will not be useless to those who may be inclined to pursue 

 the same train of investigation, to describe the means which I 

 adopted for examining the animals in question ; while it will 

 further the purpose of explaining the species of evidence by 

 which I was satisfied respecting the nature of the objects which 



