4768 . Marine Vivaria. 



Marine Vivaria. — I beg to draw your attention to a fact which, although probably 

 well known, has never, that I am aware, been published in any remarks on vivaria : I 

 allude to the fact that plants will live in water without the compensating balance of 

 animal life. My study-window faces North-east, and I have at the present time five 

 show-glasses filled with salt water, and two and. a globe filled with fresh water. The 

 following is the state of the marine portion : — No. 1 was three-parts filled, last June, 

 with water, and a few animals, that I had under examination, and some weeds placed 

 in it ; the animals s^nd weeds died : I left it still in the window, and two-thirds of the 

 water has evaporated ; there is, notwithstanding, a healthy growth of Enteromorpha, 

 and the surface is covered wilh air-bubbles: the water, as in all, is perfectly sweet. 

 No. 2 was filled in August last, and a small gurnard placed in it: as the water 

 evaporated it was filled up to its original level with fresh water; the gurnard was 

 killed by the seveie frost, and the water left: no weeds were placed in this glass, and 

 the dead gurnard was taken out: the water has evaporated to half, and there is now 

 a luxuriant growth of Enteromorpha, much thicker and more forward on the side next 

 the window. No. 3 was also filled with sea water in June last, but nothing placed in 

 it: in the course of a few days a growth of green weed appeared. In July or August 

 last I placed in it a small mullet: this mullet died near the end of the last frost, and 

 the water has been since left ; it is now covered with a growth of weed, but not to the 

 extent of the last; it has, however, a thick coating on the bottom, and a small quantity 

 of film floating on the top : the mullet fed on the weed. No. 4 was filled, in March 

 last, with weeds and a few of the smaller Serpulae and Annelides: these last I by 

 degrees took out, leaving nothing but the weeds : all these are alive and doing well, 

 and the sides of the glass jar are covered with patches of green weed ; the weeds 

 evolve oxygen in large quantities, and the top of the water is covered with patches of 

 air-bubbles. No. 5 contains water which I made putrid by throwing in dead animal 

 substances, until it became black and stunk insufferably ; I then filtered it several 

 times through filtering paper, in which was placed a quantity of powdered charcoal, 

 until I at length obtained it scentless and crystalline : I left it in a room away from 

 the window until to-day, and on examining it I find a slight growth of weed round 

 the edges of the bottom : the taste of this water is slightly pungent. In all these 

 glasses the sole animal life is a few minute Entomostraca, such as Cyclops and 

 Cypris. Now, if carbonic acid is evolved solely from animals, whence comes the 

 necessary quantity for the plants in my glasses ? The facts are exactly as I have 

 stated them ; and another fact that I have observed appears to point to a solution ; it 

 is this — if you watch the glasses during the morning, and as long as the sun does not 

 shine on them, you will find all at rest. There are the plants, and there is the water, 

 but no air-bubbles ; but watch it when the sun shines on the glass, then you will find 

 that, one after another, the little bubbles form and rise to the surface, and this lasts 

 until the rays of the sun cease to shine on the glass. Should the sun, as at this 

 present moment, be hidden by clouds, the bubbles cease forming, but to recommence 

 on his appearance. From what I have said it appears to me that I shall be justified 

 in assuming that the direct light rays of the sun possess and exercise the power of 

 forming sufficient carbonic acid, or some other chemical combination, for the well- 

 being of plants, and thus far supplies the want of animals. — William Thompson; 

 Weymouth, May 28, 1855. 



