Notes on Animals in small Aquaria. 4537 



touched by the swimming fish, — stinging them, and causing a great 

 degree of irritation ; and that the polypes were torn from their 

 position by the greater strength of the fish and carried to their places 

 of retreat, where, by consequence, the mischief was continually 

 accumulating. A similar removal from one place to another of an 

 analogous creature, the young of the Actinia, takes place in sea water, 

 from their attaching themselves by their tentacula to some moving 

 denizen, the hold being released very soon after they are forced from 

 their original attachment. 



Sea Water. Memorandum 1. — In my previous experiments in this 

 branch of the subject, commenced in January, 1852,* and of which 

 some results were communicated to the British Association at their 

 meeting last year at Hull,t I stated that the result of my experiments 

 to ascertain the kind of sea-weed best fitted for maintaining the 

 balance with the animal life was, under ordinary circumstances, in 

 favour of the Chlorosperms, and that the Rhodosperms submitted to 

 the like conditions did not answer the purpose desired and at the 

 same time retain their colour and beauty, inasmuch as they very soon 

 became coated with a growth of short green and brown Confervae 

 (Conferva tortuosa ?), which entirely mantled the whole surface of the 

 fronds and destroyed their characteristic appearance. During these 

 investigations, however, it occurred to me that it might be possible to 

 obviate this drawback, and I have, I believe, succeeded, after a series 

 of experiments, in overcoming this inconvenience, and can now retain 

 them in all their natural loveliness, and render them quite efficient for 

 all the purposes required — that is, as consumers of carbonic acid and 

 generators of oxygen. 



The ground on which I have reasoned as a basis for these experi- 

 ments has been the consideration, that nearly the whole of these red 

 or pink-coloured sea-weeds are found either in deep water or under 

 the shade of other Algae, and from the fact that they were also often 

 known to occur in shallow rock-pools : it was hence fair to assume 

 that the pressure of the column of water could not be an important 

 element in the production of these coloured growths, and therefore 

 that it must depend upon a modification of the light. Hence my 

 idea was that the effects of the depth of the water might be capable 

 of being imitated by tinting the light through the interposition of 



* 'Garden Companion,' January, 1852. 

 f ' Zoologist' for 1853, p. 4 1 18. 



