106 



SCIENCE-GOSSIP. 



[May 1, 1SGG. 



had succeeded in keeping a living marine sponge, 

 but the species and the circumstances were not 

 mentioned. 



I should name that it is not always safe to place 

 these dredged masses, when got fresh from the sea, 

 into ordinary aquaria without preparation, as there 

 are almost sure to be upon them some animals more 

 delicate than others ; and if these are below the mass, 

 between it and the floor of the aquarium, they pro- 

 bably will die, and their death spreads destruction to 

 other things around; and so, a small streamless tank, 

 with an amount of aeration barely sufficient for its 

 ordinary wants, is thus apt to become quickly and 

 injuriously affected throughout. Accordingly, when 

 in trade in London, I used, as a means of safety, to 

 be obliged, with much regret, to carefully scrape 

 and wash away all matters, however interesting, 

 from these masses except the Serpuhe themselves ; 

 and hi no other state could I sell them to my cus- 

 tomers without chance of disaster. 



Here, however, I am only too glad to get such 

 masses just as they are dredged, no matter how 

 large, or how rough, dirty-looking, and scabrous; 

 and I place them first, and for some time, in 

 great shallow probationary troughs, with a strong 

 stream of sea-water running through them day and 

 night, and I turn over the masses occasionally, so 

 as to present all their sides equally to the oxygen- 

 ating influences of the current, and to check the 

 tendency to decomposition which exists when the 

 underlying parts of the masses are in close contact 

 with the sand and shingle forming the bed of the 

 troughs. When this is done, and all is healthy, and 

 there seems nothing else likely to die, the masses 

 are transferred to the show-tanks, and when any- 

 thing grows up upon them in the manner described, 

 I am very particular in keeping it in exactly the 

 same spot as that hi which it made its appearance, 

 as often a removal of but a few inches disturbs some 

 delicately-balanced conditions, and a sudden disap- 

 pearance is the result. 



The mention of sand and shingle in aquaria re- 

 minds me that some early writers on the subject — 

 the Rev. Messrs. Kingsley and Tugwell, for ex- 

 ample — advise that no sand or shingle should be in 

 aquaria, as they encourage the formation of the 

 blackness which is a sign of the presence of sul- 

 phuretted aud carburetted hydrogen gas, resulting 

 from the decay of organic substances. Fine sand 

 is even worse than coarse, as the particles lie so 

 closely together, and around any object resting upon 

 or in it, that water cannot freely circulate around. 

 But the discomfort to the animals, and the unsight- 

 liness of a bare slate or glass bottom in a tank, by 

 far outweigh any advantages to be derived from the 

 absence of sand and shingle ; and, indeed, no black- 

 ness will form unless some decomposing substance 

 is carelessly suffered to remain in the aquarium ; 

 and when that is the case, its removal, and the 



gentle stirring up of the sand at the spot affected, 

 will cure the evil in a short time. And as to the 

 black layer which mil always in time accumulate at 

 the bottom of the layer of the gravel, below its sur- 

 face, and which cannot be prevented by any amount 

 of good management, and which it is probably not 

 desirable to prevent, as many animals seem not to 

 dislike it by the manner in which they burrow in it, 

 — that is harmless, so long as it does not crop 

 through the surface. 



I have to remark, that Mr. Shirley Hibberd, in last 

 November's number of Recreative Science, advises 

 aquaria to be built up internally with old oyster-shells 

 which have for a longtime previously been exposed 

 to wind, rain, and drought, to destroy any germs 

 of animal life happening to be upon them, and 

 which, by decaying, would prove hurtful to other 

 things. But this killing of all germs would deprive 

 the shells of the only value they can possess, as 

 they then would have no more worth than any 

 other rough substances for the growth of alga upon 

 them ; and it is contrary to good taste to intro- 

 duce dead shells in an aquarium merely because 

 they are shells, or because they are rough. Rough 

 stones would be much better, and more natural- 

 looking. W. Alford Lloyd, 



Zoological Gardens, Hamburg. 



PIN CENTRES AND ROSE CENTRES. 



IE any one will take the trouble to examine a bank 

 of primroses, it will be seen that the flowers 

 are by no means all alike. There is a great variety 

 of colour : here and there one almost pure white ; a 

 few almost lemon-yellow, with every possible shade 

 between. They differ, too, in their form : some 

 having a starry appearance, because the segments 

 of the flower are narrow ; others looking solid and 

 round, on account of the segments being broad and 

 lapping well over each other, and these last are by 

 far the handsomest flowers ; so that, if one wished 

 to transplant primrose roots into a garden, the 

 trouble of selecting plants would be well repaid in 

 the effect produced. 



But there is, physiologically, a much more im- 

 portant difference in primrose flowers than either 

 the colour or the form. On some roots the flowers 

 have the pistil much longer than the stamens ; on 

 other roots the stamens are much longer than the 

 pistil. In the first case there will be seen the pistil, 

 resembling a pin's head just within, or even pro- 

 truding from the throat of the flower, no stamens 

 being visible, because they are situated low down 

 in the tube of the corolla. In the second case, the 

 stamens are seen forming a pretty coronet, which 

 closes up the throat of the flower, entirely hiding 

 the pistil, which, indeed, does not reach more than 

 half way up the tube of the corolla. 



