98 



HARDWICKE'S SCIENCE-GOSSIP. 



[May 1, 1S69. 



his double (dividing) head, set his wheels in motion, 

 to the delight of the observer, when suddenly he 

 would stop them, pause, as if listening to the ap- 

 proval, shake his heads in a most ludicrous manner, 

 then suddenly disappear within his castle to return 

 after a time and repeat the performance. My 

 drawings further record the presence of Actinophrys 

 sol, Amsebse, the slow-stepping water-bear, some 

 of the less common diatoms clinging to the rock- 

 work and weeds, two or three species of desmids, 

 and plenty of the Algse with their moving spores. 

 I witnessed numberless cases of their singular re- 

 production, some no doubt normal, and sufficiently 

 curious, others so remarkable that it would have 

 been strange indeed if a malformation, or, as some 

 would say, a variety, had not been the result. All 

 the last-described forms were as abnormally (?) 

 large as the Rotifers, and it really required more 

 than a hand-magnifier to see them to perfection. 



I wish it to be understood that the vegetable and 

 lower forms of animal life retained a uniform 

 character during the three years. Not so the 

 Rotatoria. A different species had the ascendency 

 each year — a remarkable fact for which I cannot 

 satisfactorily account : it was certainly not due to 

 any alteration in the management of the aquarium. 

 Once and again I supplied my friends with weed 

 and water, and I started several juvenile aquaria 

 myself, with the hope of being better able to watch 

 the habits of my live stock; but they would not 

 take kindly to their new homes, and generally 

 vacated within the fortnight. At the end of the 

 third year these beautiful creatures vanished, " like 

 the baseless fabric of a vision," and have never 

 since returned. I often wondered why they re- 

 mained so long, their frailty being such that only 

 the wisdom of an Almighty Creator could adjust 

 means to an end so delicate as to insure their 

 preservation. 



It seems to me that the following questions are 

 suggested by the facts I have related ; and that on 

 the correct answers to these questions will depend 

 the success of any one who tries to produce a like 

 result : — 



1. How did the organisms described get into the 

 aquarium, previously barren of anything of the 

 kind, and live and propagate for so lengthened a 

 period ? 



2. What was the cause of their increasing in 

 such unaccountable numbers, in a space so com- 

 paratively small ; and how came they so unusually 

 large in size ? 



3. Where is to be found the reason for one species 

 of the Rotatoria being more abundant one year than 

 another ? 



I will give my answers to the two first of these 

 questions. They may not be correct ; but may help 

 others to find the true ones. As to No. 3, 1 fail to 

 make a rational guess. 



1. It is my custom to throw all suitable gather- 

 ings from the various localities I visit, when I have 

 otherwise done with them, into my aquarium, and 

 let the weed remain for a week or so, and then 

 remove it. A collection made on a charmingly fine 

 early spring day of the first of the three, years, from 

 a pool half covered with Ranunculus aquatilis in 

 bloom, was so treated. I could scarcely have failed 

 in detecting Rotifers on this weed had there been 

 any; but a few of their statoblasts would easily 

 escape notice. I believe, therefore, that I got 

 them in this gathering, especially as I noticed that 

 the creatures were far more plent iful on the Ranun- 

 culus than on other weeds. But others, and myself 

 subsequently, have knowingly put the tube-bearing 

 Rotifera into their tanks only to see them die out in 

 a week or two ; why, then, did those under notice 

 become acclimatized and prosper? Because the 

 statoblasts, and not the adult animals, were used ; 

 and those were gathered so early in the year that 

 the change did not affect them. I have two facts in 

 support of this — the failure in the attempt to stock 

 either my friends' or my own tanks with the adult 

 animals with the unusually fine and healthy spe- 

 cimens at my command; and the statement of a 

 correspondent in the "Annals of Natural History," 

 some years after I had formed this opinion, to the 

 effect that he never failed to stock his aquaria 

 with freshwater polyzoa, if he obtained for that 

 purpose the statoblasts on some fine winter's day, 

 or early in the spring, but could not succeed with 

 the mature animals. 



2. At the time when our Rotifera and their 

 retinue made their appearance, I was watching the 

 habits of certain freshwater fish, and paid great 

 attention to their commissariat department, taking 

 care that they had plenty to eat. This consisted, 

 chiefly, of white of egg and vermicelli soaked in 

 water. Now, I believe in the cloud of minute 

 particles given off by the latter, and fragments 

 from the eggs, my visitors found a bountiful and 

 suitable table, and they were content. I ceased to 

 keep the fish in the summer of the third year, and 

 the vermicelli, &c, was discontinued : you already 

 know that it was in that year the animal life • 

 entirely died out. It now only required the 

 application of the general law of abundance or 

 scarcity of the necessary conditions of life to under- 

 stand why they increased so rapidly, and were such 

 model specimens of their kind, and as suddenly 

 disappeared. 



No arguments are needed to prove how much 

 pleasure I had, or how much knowledge I gained, 

 during the three years' stay of my lowly friends. 

 That you may not forget it, I again repeat, that 

 what has been done may be done again. Go and 

 try, and let us know the result. 



W. H. Hall. 

 South Hackney. 



