between Animal and Vegetable Organisms. 4119 



it was impossible to make the red weeds answer the purpose, as he 

 had tried them, and strongly recommended the olive or brown- 

 coloured Algae ; while, again, others thought that 1 should be more 

 successful with those which had in theory first suggested themselves 

 to my own mind, namely the Chlorosperms. After making numerous 

 unsuccessful experiments with both the brown and the red varieties 

 of Algae, 1 was fully convinced that, under ordinary circumstances, the 

 green weeds were the best adapted for the purpose. 



This point having been practically ascertained, and some good 

 pieces of the Enteromorpha and Ulva latissima in a healthy state, 

 attached to nodules of flint or chalk, having been procured from the 

 shore near Broadstairs, several living animal subjects were introduced 

 together with the periwinkle. Everything progressed satisfactorily, 

 and these all continued in a healthy and lively condition. 



My first trials were conducted in one of the small tanks which 

 had been used for fresh water ; but as it was necessary, during the 

 unsuccessful experiments with the brown and red sea-weeds, to agitate 

 and aerate the water, which had been rendered foul from the quantity 

 of mucus or gelatinous matter generated during the decay of their 

 fronds, until the whole had become oxidized, and the water rendered 

 clear and fitted for another experiment, it was, therefore, for greater 

 convenience, removed into a shallow earthen pan and covered with a 

 large glass shade to protect the surface of the water, as much as pos- 

 sible, from the dust and soot of the London atmosphere, and at 

 the same time impede the evaporation. In this vessel then I had 

 succeeded perfectly in keeping a large number of beautiful living spe- 

 cimens in a healthy condition up to the close of 1852. I therefore 

 gave instructions for the making of a small tank as a more permanent 

 reservoir, and one more adapted for carrying on my observations and 

 investigations on the ceconomy and habits of the inhabitants. 



From the experience I had obtained in my experiments with the 

 freshwater tank, I was induced to modify slightly the construction of 

 this vessel ; thus, at the back, or part towards the light, the framing 

 was filled with slate in the same way as the ends and bottom ; for I 

 had found that the glass, originally employed, very soon became 

 covered with a confervoid growth which had an unpleasing appear- 

 ance to the eye, and in consequence of which I had been obliged to 

 paint the glass on the exterior to prevent this growth from increasing 

 to too great an extent. It was also an unnatural mode of illumination, 

 as all the light should pass through the surface of the water. The 

 front towards the room and the observer was constructed of plate 



