Plants alive in unchanged Sea-water. 267 



Crisia denticulata, a large tuft. 



Coryne ?, young. 



Pedicellina Belgica, two numerous colonies. 



Membranipora pilosa. 



Doris {bilineatat). 



Polycera 4i'lineata, very small. 



Phyllodoce lamelligera, about 11 inches long. 



A coil of small Annelides. 



Several Serpulce, 



Acaridce. 



Entomostraca. 



Infusoria. 



Grantia nivea. And other smaller zoophytes and sponges 

 which I could not identify. 



Soon after this examination I went on a journey, and did not 

 return till the 7th of July. The weather had set in very hot : 

 whether this, combined with the closeness of the room, had had 

 any effect I do not know ; but on my return I found the water 

 beginning to be offensive, a sort of scum forming on the surface, 

 and the animals evidently dying. Some were already dead, but 

 most of the others recovered on being removed to fresh sea- 

 water. This result, though it put an end to my experiment at 

 that time, I do not regard as conclusive against the hypothesis ; 

 for of course animals are liable to death under any circum- 

 stances, and the corrupting body of one of these in so limited a 

 volume of water would soon prove fatal to others, even though 

 there might be no lack of oxygen for respiration. It is possible 

 that one of the large Actinia may have casually died during my 

 absence, the timely removal of which might have averted the 

 consequences to the others ; but this is only conjecture. Perhaps 

 there was too large an amount of animal life in proportion to the 

 vegetable ; but the maintenance of all these in health and acti- 

 vity for nearly nine weeks seems hardly to agree with such a 

 supposition. 



I have always found one of the most unpleasant phsenomena 

 in the experiments to be the appearance, in the course of 

 a few weeks, of greenish or yellowish matter about the sides 

 of the jar, hindering their transparency. This I have reason 

 to think is the early state of Confervoid plants, for filaments of 

 green Confervse soon begin to shoot from this accumulation, and 

 would probably choke up the water in time. Mr. Warington's 

 suggestion of employing the phytophagous Mollusca to get rid of 

 the accumulating vegetable matter, had not occurred to me ; it 

 is ingenious, and might perhaps obviate this inconvenience. I 

 had myself observed that the presence of some of the Trochi 



