Luminous Ammah. , 251 



ject ; and the addition of a few more will not be misplaced 

 to those who have not hadany experience in these investigations. 



These animals always abound most, with few exceptions, in 

 the smallest harbours, and, more particularly, in narrow creeks, 

 among rocks or under high cliffs, where the water is sheltered 

 from the sea and wind, and where it is consequently seldom so 

 much disturbed as in more open places. A large proportion of 

 them indeed seems to be exclusively limited to situations of this 

 nature, being never found in the open sea nor far from shore. 

 Many of the minute marine animals also appear to affect exclu- 

 sively those shallow and rocky situations where sea weeds 

 abound, and which are equally the favourite haunts of many larger 

 species, such as nearly the whole tribe of crabs, and many 

 others which it is unnecessary to enumerate. 



It is in such places then, and at such times, that is, in narrow 

 and rocky creeks or weedy shoals, and in calm weather, that 

 the naturalist will meet with most success ; and it is in such 

 circumstances also that the water will be found most luminous. 



That it does not always appear luminous in calm weather, 

 and when the vessel is quiet at anchor, is however certain ; and 

 it is this which has conduced to mislead observers respecting 

 the causes of the light, as well as to lay the foundation of fal- 

 lacious prognostics regarding the weather. It requires agi- 

 tation to elicit the light of these animals in abundance ; and as 

 this naturally happens in troubled water, they have been sup- 

 posed to abound in gales of wind and in a breaking sea, when 

 they are, in fact, comparatively scarce. In calm weather, 

 crowds of medusae or other very luminous species, will often be 

 floating around, yet betraying themselves only by an occasional 

 twinkle ; when any disturbance communicated to the water is 

 sufficient to involve the whole in ablaze of light. 



I formerly remarked, that the luminous action was voluntary; 

 and this opinion has been amply confirmed by further attention 

 to the animals possessed of this property. Among millions of 

 these, of numerous species, the usual actions of locomotion will 

 be performed for hours, or for a whole night, without the slightest 

 indication of their presence ; or perhaps some individual will 



