Mr. C. S. Harris on the Marine Vivarium. 133 



dant, and make a fine show among a group of common Ac- 

 tinia. 



I never found that the green plague could be kept down by 

 the introduction of the common Winkle, or other Mollusca. It is, 

 however, highly interesting to see the latter deposit their spawn ; 

 and moreover the Trochi and others are very beautiful. One 

 very interesting fact I witnessed several times : the Gonoderus 

 (I know not the specific name) deposit its spa\vn, in the form 

 of a mass that I can compare to nothing better than a shirt frill, 

 and always quite at the edge of the water. I had two in the viva- 

 rium : when one, which I suppose to be the female, had deposited 

 its spawn, the other took its place close by, as if to guai'd it. I 

 removed them several times to the opposite end, but they could 

 be seen as constantly returning to the same spot : as they chose 

 such an unsafe place, I had no opportunity of seeing the result 

 of their labours come into life. 



The Actinia dianthus will appear sometimes covered with a 

 thread-like mucilage, which in a few days shows small joints or 

 knobs ; these begin to wave or float about and attach themselves 

 to the glass, or shells and rock, and in a day or two, if examined 

 with a lens, will be found to be the young Actinia ; therefore 

 with common care you need not be without this lovely variety, 

 which in fact gives no trouble. 



It is only within the })ast two years that I have heard of 

 attempts to keep sea water pure by means of certain sea-weeds ; 

 but I must confess that all the vivaria I have seen since, where 

 the attempt has been made, have been anything but pleasant sights 

 to look upon, — not in the least resembling the clear rock-pools one 

 delights to pry into on a bright summer's day. Whether such 

 a desirable thing will ever be accomplished, is a question far 

 from being solved ; I have made two or three attempts, at the 

 suggestion of others, but without success. In warm weather up 

 rose that plague, the little green weed, and soon hid everything 

 from sight ; thus destroying the use of the vivarium as an object 

 of study or delight, though by it the water might be kept pure, — 

 but how far animal life also, I know not. I certainly think, 

 as a pubhc sight, instructive and entertaining, the vivarium is 

 best kept in order by manual labour, changing the water, clean- 

 ing the animals, rocks and shells, and removing instantly all 

 that perish. An hour or so in early morning is all that is required, 

 with the introduction of a few new or fresh objects from time to 

 time ; and by occasionally changing the masses of rock, — from 

 which change you would get much proper food for youi- animals, — 

 all would be kept in a healthy condition. In large tanks larger 

 rock-lish may be admitted ; but, I think, as a rule, all that have a 

 tendency to foul the water should be kept apart, among which are 



