38 



HA , RD WICKE 'S S CIENCE - G OSSIF. 



night ; pour off again, and go on so for at least a 

 week. At the end of that time we shall generally 

 find we have a pint of pretty thick sediment without 

 the admixture of any fibres that might come from a 

 muslin strainer." 



ZOOLOGY. 



Marine Aquaria. • — I always read with great 

 interest the occasional contributions of your corre- 

 spondent "G. S." on the management of Marine 

 Aquaria ; but there is one point which she strongly 

 insists upon, respecting which I cannot entirely agree 

 with her ; I allude to change of water. That a system 

 of frequent and entire renewal of water is bad, I will 

 freely admit, causing as it does sudden changes of 

 temperature and density, which will often prove fatal 

 to delicate animals. But an occasional partial renewal 

 — say, to the extent of one-fourth or fifth of the bulk of 

 water, if carefully and judiciously made — I have found, 

 in an experience of nearly twenty years' successful 

 aquarium-keeping, to be productive of the best results. 

 I haveforyears been in thehabitofdravvingoff a portion 

 of the contents of my aquaria — say, once in three or four 

 months, and replacing with fresh sea-water previously 

 allowed to stand for twenty-four hours to settle, and 

 I see no reason to be dissatisfied with the practice. 

 On the contrary, I always find that for some days 

 afterwards the anemones open better, and the fish 

 and Crustacea are more lively and vigorous. That 

 this should be so seems to be consistent with reason 

 and the laws of nature. The animals we keep in 

 aquaria are mostly of shore-haunting species, and are 

 accustomed in a state of nature to the regular ebb and 

 flow of the tide twice in something over twenty-four 

 hours. This source of health and nutriment they are 

 entirely deprived of in confinement ; hence the de- 

 terioration which most of them gradually show in 

 even well-managed aquaria. It is indeed often a 

 matter of wonder to me that, considering the immense 

 change of the conditions of life which aquarium 

 animals experience in the transfer from the sea to our 

 tanks, we are able to keep them in as good health as 

 we do. Anything like a periodic tidal flow is, of 

 course, impracticable in any but large public aquaria, 

 and in small private tanks the trouble incurred is 

 generally an obstacle to a frequent exchange even from 

 a resene stock of water, however beneficial this might 

 be. It therefore seems to me a pity, for the sake of a 

 hard-and-fast rule, to debar our captives from the 

 evident enjoyment and increased vigour imparted by 

 an occasional supply of water fresh from their native 

 sea. — Edward Ilorsnailc, Dover. 



Embryology of Fish. — Dr. Gunther, the well- 

 known ichthyologist, has recently discovered that the 

 young of the Sword-fishes and Chretodons differ in 

 structure very much from the adults. In the young 

 of Chretodon the front of the body is shielded with 



large bony plates. In those of the Sword-fish the 

 scapular arch is prolonged into a horn at the lower 

 part, and the ventral fins are absent. No "sword" 

 is possessed by them, but the jaws are long, and are 

 both armed with teeth. As the Sword-fish grows, 

 the upper jaw gradually alters, and the "sword" is 

 formed. 



"The Popular Science Review."— Tlie Janu- 

 ary number of this favourite review commences under 

 new editorship, Mr. W. S. Dallas, F.L.S., having 

 replaced Dr. H. Lawson in the editorial chair. The 

 present number is a capital one, and includes papers 

 by the Rev. W. S. Symonds, entitled, ' ' Among the 

 Volcanoes and Glaciers of Auvergne " ; another by 

 Professor F. W. Rudler, F.G.S., which will be 

 largely read, inasmuch as it exposes one of the 

 "dodges" practised at some watering-places, on 

 " Agates and Agate-working " ; an article (we pre- 

 sume by the Editor) on " Echinoderms " ; a paper 

 by Mr. E. G. Ravenstein on "The Arctic Expe- 

 dition," &c. The articles are well and abundantly 

 illustrated ; and besides them we have the usual 

 monthly summary of progress in the various sciences, 

 physical and natural, as well as cleverly-written and 

 telling reviews of new books. 



Bathybius. — It will be remembered that the re- 

 searches of the naturalists on board the Challenger 

 threw great doubt on the reality of Bathybius as an 

 organism. Dr. Bessels, of the Polaris Expedition, 

 however, states that he discovered in Smith's Sound 

 a form exactly like Bathybius, only a simpler struc- 

 ture (?), to which he has given the name oi Proto- 

 bathybius. 



Cribella rosea, Muller. — In a publication of 

 Cork Cuvierian Society, entitled "Contributions to- 

 wards a Fauna and Flora of the County of Cork, read 

 at the Meeting of the British Association held at 

 Cork in the Year 1843," Youghal is given as a 

 station for C. rosea. In 1868 I gathered specimens 

 of this echinodenn at Church Bay, outside Cork Har- 

 bour, at the low tide-mark, among the rock-jjools, 

 along with Uraster glaeialis, Linn. ; U. violacea. 

 Mull., and Palmipes membranaceus, Retz. In the 

 following year I saw several specimens lying on the 

 shore after a storm near the Old Head of Kinsale. — 

 H. J. Ryder. 



The Insects of the Arctic Expedition. — 

 Mr. M'Lachlan has remarked, in the Entomologist'' s 

 Alonthly Magazine, on Captain P'ielden's collection of 

 the insects of the Arctic expedition. The greater 

 number of the insects were collected near Discovery 

 Bay in 81° 42' N. latitude ; some of the Lepidopte)-a 

 are even from 82'' 45'. The most interesting fact is the 

 occurrence of five or six species of butterflies within 

 a few hundred miles of the North Pole, especially 

 when taken into consideration with the fact that Ice- 

 land and the large islands of the Spitzbergen group, 



