These, then, are the principal circumstances with re gard to the animals themselves, which the naturalist should have in view in his attempts to investigate the wa ter of the sea, for the purpose of discovering the luminous animals which it may contain, and for satisfying himself that our statements are correct. In this way, also, he will succeed, and in this only, in discovering the mere ex istence and nature of these animals, as well as in ascer taining the fact of their luminous nature. The more par ticular directions respecting individuals we shall give im mediately. Besides these deductions, however, the fore going facts will serve to add something to our knowledge respecting the natural history of these much neglected animals generally ; for that they have been much neglect ed we hope shortly to prove. But should these remarks serve no other purpose, they will serve to assist others, as they did ourselves, in these examinations. They are de ductions made from our own repeated experience, and they will probably serve to prove most fully to others, what we ourselves think completely ascertained, namely, that luminous animals abound in the waters of the ocean, even when, from their minuteness, from their not actually emitting light, or from other causes, they are least sus pected ; and that the property of phosphorescence is grant ed to every one of these neglected inhabitants of the deep.
It is now necessary to point out somewhat more parti cularly the method used in examining these animals, so as to enable us to decide on the luminous property of any spe cies.
With respect to the larger kinds, there is seldom any difficulty. With sufficient care, a large medusa, a bcroe, a nereis. or any of the distinctly visible animals, may be secured in the very act of emitting light, and then examin ed at leisure. Should not an animal, as is usual, extin guish its light as soon as it is taken, it is only necessary to place it in a sufficiently large receptacle of water, and to leave it for some hours at peace. On then agitating the water, or irritating it slightly, it will immediately show its light, so as fully to remove all doubt from the observer's mind. If more than one species of these should occur to gether, they are easily separated, and afterwards examin ed. When the species are smaller, and more numerous, and where many kinds occur together, it becomes a much more difficult task to satisfy ourselves that all the indivi duals are luminous. Yet, even in this case, by sufficiently multiplying the examinations, we may approximate at least to something like accuracy; while, where a property like this is observed in so many instances to exist, and where it has probably been conferred for certain universal purposes, which we shall hereafter point out, it is not a rash conclusion to infer that no species is exempt from the general law, or deprived of this power ; since, in all essential circumstances, the habits and pursuits of these marine animals are the same.
In making these observations, at least in a small vessel, it is requisite that the water should be calm ; as any agita tion of the ship renders the investigation impossible, from the motion of the observer's person, as well as that of the water under examination. It is difficult enough, un
der the most favourable circumstances, to catch and retain the smaller species within the focus of the lens. They are themselves nc less rapid and restless in their 'move ments than they are minute ; so that he who is determined to investigate them must not only be freed from all unne cessary inconveniences, but he armed with no small share of patience. When such examinations can be made on shore, it is most convenient ; but in this way we are very much limited as to the number of species, as many of them arc only found at considerable distances from the land. In the deep harbours and sea-lochs of our own country, we can generally both examine them easily, on account of the smoothness of the water when at anchor ; besides which it will be found that their situations present a very great variety.
There is something in their localities, which, though not ascertained fully, appears constant at least within cer tain limits, independently of mere climate. As to this latter circumstance, we have reason to believe, from the observations of the very few navigators who have attended to this subject, that many species exist in the ocean, in the polar, the temperate, and the tropical seas, which are confined to those particular tracts, as arc the larger fishes of the same regions. Yet this subject has met with so little attention, that we can scarcely give the description or name of any one species of the minuter kind. That our readers may be enabled to judge of this neglect, we need only say, that in the space of six summer weeks on our own coasts, we have examined upwards of two hundred different animals, and that of these not less than two-thirds were undescribed species.
We have no doubt that we could have tripled our own list in one season, had this formed a principal pursuit, in stead of being, as it was, only an incidental amusement for idle hours; and have every reason to suppose that we should even then have been very far short of knowing those which belong to our seas. Our readers who reflect on the infinite variety of larger marine animals which have been discovered in various parts of the world, may well conceive the numbers of these also that would have been ascertained, had naturalists, favoured with such opportu nities for observation, paid greater attention to a subject which they seem to have almost universally agreed in neglecting. Excepting the labours of Muller, there is not much that is worthy of notice in the writings of natu ralists on this subject ; and even he appears to have been far from suspecting the existence of numerous species that must have passed through his hands. Of animals. purely microscopic, we scarcely find ten that have been described by all naturalists united ; and, in a single bay of the Highlands, we have found twice as many in one even ing. We mention these circumstances, not to boast of our discoveries, since we scarcely consider ourselves as deserving to be ranked among this class of naturalists ; but with the hope of stimulating the curiosity and activity of those who have the means of consistently pursuing a train of investigation, which, to us, was purely accidental.