4534 Notes on Animals in small Aquaria. 



Memorandum 2. — As an evidence of the permanency of the balance 

 capable of being established between the animal and vegetable organ- 

 isms by the introduction of the water-snail or other phytophagous 

 mollusk, as I have elsewhere described,* I may state that the same 

 water in which my original experiments were made in March, 1849, 

 has been in continual use up to the present time, several fish living 

 constantly in it, without disturbance, and that it is now as bright and 

 in as healthy a state as at the first period of its being employed. 



Again, in a small jar of about one pint capacity, having a single 

 plant of Vallisneria spiralis growing healthily in it, and with a few 

 small water-snails as scavengers, I succeeded, during the spring of 

 1853, in hatching and rearing a young trout. The egg was obtained 

 from Mr. S. Gurney, jun., and had been removed from his preserves 

 in the river Wandle ; the shell ruptured the day after my receiving it, 

 and it was maintained in a perfectly healthy state during the whole of 

 the period required for the development of the respiratory organs, and 

 the complete though gradual absorption of the ovum. This develop- 

 ment was perfected in fifteen days from the bursting of the shell, till 

 the period that the fish could sustain itself contiuously in the water 

 and was able to swim strongly. Having arrived at this stage of 

 maturity, the vessel became far too small for the free use of its active 

 powers of locomotion, and it was therefore transferred to a small tank 

 containing several minnows, when, to my great annoyance, it was 

 immediately seized and devoured. 



As another instance of the voracity of the finny tribe and their 

 destruction of each other, I may mention here that I had on a 

 previous occasion placed several small trout fry over-night in an 

 aquarium containing some gold-fish, but they must have been rapidly 

 preyed upon, as no trace could be seen of them the following morning. 

 These facts will demonstrate clearly the havoc which must take place 

 in the rivers and streams among the young fry of various fish under 

 ordinary circumstances, when they are proved to be devoured with 

 such extraordinary rapidity even by such species as the gold-fish or 

 carp tribe and the minnow. 



Memorandum 3. — Care should be taken in the aquarium for fresh 

 water to exclude the ordinary polype or Hydra fusca, particularly 

 where certain species of fish are to be preserved, as with the minnow 

 (Lenciscus Phoannus), for these creatures, insignificant as they may 

 appear, after a short time cause their death, and that under most 



* Published in the ' Zoologist' for 1850, p. 28C8. 



