122 SEA-WATER AQUARIA. 



passage : — " And now, as I have poked fun at these antediluvian 

 aquarium sea-weed gatherers, I should like to say something 

 which is not fun. I have already mentioned that the collecting, 

 transmission, and introduction of them was a very obvious appli- 

 cation of the balancing arrangement of plants and animals, and 

 there would have been nothing to say against it on the score of 

 being lumbering, costly, or anything else, // these sea-weeds would 

 live in captivity as well and as easily as the animals which these 

 plants were supposed to keep in health. But they would not live, 

 they will not live now. And then, to add to the provocation of 

 the matter, they will sometimes live and thrive, perhaps one time 

 in a hundred, or one time in a thousand, when one takes no 

 pains at all with them, and die outright immediately when they 

 are made the subject of goodness knows how much solicitude." 



The fact is, as Lloyd found out for himself, that if the water 

 (whether salt or fresh) is left in an aquarium without being 

 changed, and exposed to light, a low form of vegetation ialgcE) 

 will develope on the rock-work and glass from invisible germs 

 existing in the water ; and this vegetation — which grows naturally, 

 and is adapted to the circumstances of an aquarium — is amply 

 sufficient for all purposes, so that there is not the slightest 

 necessity for the introduction of young or full-grown aquatic 

 weeds from without. 



So, after my failure with Ulva latissima, I made no further 

 attempt to introduce and cultivate sea-weeds in my tank, but let 

 the water rest for a time, exposed to a moderate light, not even 

 circulating it, and of course not changing it. In a few weeks, 

 sure enough, there developed on the glass, and on the rock-work, 

 both green and brown vegetation. The green grows chiefly on 

 the glass and the exposed portions of the rock-work which face 

 the light from the window, whereas the brown growth appears on 

 the submerged rock-work, and on parts more in the shade. This 

 vegetation exists mostly in the form of a coating over the parts 

 which it favours, but on the lower portions of the rock-work, 

 tawny filaments, half an inch or so in length, shoot up in tufts, 

 and from these, when the sun shines on them, streams of bubbles 

 may be seen rising upwards through the water. 



I cannot refrain from giving a quotation bearing on this sub- 



