Mollusks. 5369 



posed morsel of leaf has disappeared ; the green piece still remains in 

 the same condition as before. 



April 22. The cotyledons remain in the same condition, they have 

 not put forth any true leaves. 



June 2. One of the seed-plants and also the little piece of green 

 leaf have disappeared; the cotyledons of the other seed-pfant are 

 rotting away. 



June 8. The remaining plant has vanished. The Mollusca have 

 been dying one by one during the months that have passed ; by 

 agitating the bottle, &c, I can procure signs of life from only three, 

 namely, one Valvata piscinalis and two Valvata cristata. 



August 6. Have been absent during the past month. It appears 

 that only one Valvata cristata remains alive. 



October 8. Up to this time, just a year and a day or two since I 

 filled my bottle at the Woodeaton brook, the Valvata cristata has cer- 

 tainly been alive ; as it is now, however, dead, I have opened the 

 bottle, and turned the water out into a saucer, in order to examine 

 and count over the shells. To my astonishment but delight the young 

 Bithinia tentaculata, which has given no sign of life for many months 

 past, is nevertheless still alive ; all the rest are dead. Having removed 

 the empty shells, I have replaced the water with the Bithinia in the 

 bottle and recorked it. 



November 15. The Bithinia tentaculata is still alive. I have 

 removed the cork in order to taste the water, which is as clear as 

 crystal; it is perfectly pure and good — I should consider myself 

 very lucky had I never to drink worse ! 



We have here some very remarkable facts for our consideration ; 

 but, before saying anything on them, it may be well to mention 

 certain conditions which I am of opinion were absolutely essential to 

 the attainment of the results arrived at. 



1st. The water was of the purest kind, taken from a swift-running 

 bubbling stream, so that it was thoroughly aerated when placed in the 

 bottle. 



2nd. The bottle has been always kept in a dark place, a cupboard 

 in a wall, where the temperature is very equable : had it been placed 

 in a warm place, or where it was under the stimulus of sunlight, there 

 cannot be the slightest doubt but that the chemical changes would 

 have taken place that would have at once destroyed life. 



3rd. I would wish notice to be taken that the Mollusca were cap- 

 tured at a season of the year when it is probable the vital functions 

 were not in great activity : had they been incarcerated at a time when 

 XV. E 



