SCIENCE-GOSSIP. 



MICROSCOPY 



CONDUCTED BY J. H. COOKE, F.L.S., F.G.S. 



To whom Notes, Articles and material relating to Microscopy, 



and intended for Science-Gossip, arc, in the first instance, to 



be sent, addressed "/. H . Cooke, Thorndalc, Lincoln." 



Discolouration of Flowers. — The discoloura- 

 tion of flowers and algae on drying is attributed 

 to atmospheric ammonia. To counteract its 

 injurious effect, Nienhaus has used pressing-paper 

 previously saturated with a one per cent, oxalic 

 acid solution, and dried, obtaining in this way 

 beautiful specimens of some of the most difficult 

 flowers to preserve, unchanged. 



Eggs of Insects as Objects for the Micro- 

 scope. — The collection, preservation and examina- 

 tion of the eggs of insects will afford the micros- 

 copist many an hour's interesting recreation. 

 Curtains, carpets, floor-crevices, cushions, furs and 

 woollen garments will serve as a prolific hunting- 

 ground indoors ; while out of doors the surface- 

 waters of ponds and water-butts, the crops of 

 birds, the skins of cattle, and the leaves and 

 branches of the shrubberies will give an abundance 

 of material. Among those insects whose eggs 

 make the most interesting microscopical mounts 

 may be noted the common house-fly, the wasp, the 

 tortoise-shell and the cabbage butterflies, the 

 mottled umber and the puss moths, the dragon-fly, 

 and most of the parasites. The eggs of these are 

 of all shapes, hexagonal, conical, oval, spherical, 

 and are most richly and harmoniously coloured ; 

 while the elaborately sculptured surfaces are 

 hardly excelled in the beauty of their designs by 

 the symmetry of the ciliated, winged and fringed 

 ornamentations with which they are surrounded. 



Enemies of Oysters. — The sudden disappear- 

 ance of oysters from places where they were 

 formerly numerous may be, in part, explained by a 

 recent remarkable visitation in the harbour of 

 Sydney, New South Wales. The water, in places, 

 suddenly assumed the colour of blood. This proved 

 to be due to the invasion or rapid development of 

 a microscopic Glenodium, which, in a few days, 

 destroyed half of the animals near the land, and 

 seriously injured the oyster-beds. 



The Life-history of an Aphis, — In " The 

 Strand Magazine " Mr. Grant Allen has con- 

 tributed an interesting article on this curious insect. 

 Rose-growers and microscopists are equally its 

 enemies, but they are the least of the legion that she 

 has. From within and from without she is cease- 

 lessly being attacked by a host of belligerents. The 

 most destructive of these are no doubt the lady- 

 birds, which, both in their larval and in their winged 

 form, live almost entirely on various kinds of 

 green-fly. This practical fact in natural history 

 is well-known to the hop-growers, for the dreaded 

 " fly " on hops is an aphis ; its abundance or other- 

 wise governs the hop market, and Kentish farmers 

 are keenly aware that certain particular lady-birds 

 eat the " fly" by millions, on which account they 

 protect and foster this ladybird, thus leaving the 

 two insects to fight it out in their own way between 



them. But the aphis has a still more insidious 

 though less dangerous foe — an international parasite 

 which lays its eggs inside the body of the bud- 

 producing female. Then the grub hatches out, and 

 proceeds to eat up its unwilling hostess, alive, from 

 within. The lodger after eating his hostess out 

 eats himself out into the open air through her 

 empty skin. If you look out closely for such 

 haunted green-flies inhabited by a parasite, most 

 otten an ichneumon fly, you will find them in 

 abundance on the twigs of rose-bushes. They 

 have a peculiar swollen, quiescent look and a 

 brownish colour. Another enemy who attacks the 

 aphis with the ferocity of a tiger is the larva of the 

 wasp-fly. It is a savage carnivore, who moors 

 himself by his tail-end, stretches out to his full 

 length and swoops down on his unsuspecting prey 

 from above, and, being blessed with a good appetite, 

 he can get rid of no fewer than 120 aphides in an 

 hour. It is estimated that he can manage to 

 dispose of about 15,000 or 16,000 victims at a 

 sitting. 



A Hint. — Glycerine is one of the most useful of 

 mounting mediums, but a difficulty is usually 

 experienced with it when ringing. This may be 

 overcome by using gum damar dissolved in benzo- 

 line instead of the usual gold-size. 



Microscopical Studies. — In reply to several 

 correspondents who have asked for information 

 relative to the issue of a series of microscopical 

 studies, accompanied with text, we regret to say 

 we can give no assistance at present. In the 

 eighties, Mr. J. D. Ady issued a series of peno- 

 logical studies, with text and plates, and in biology 

 the "Popular Microscopical Studies" of Cole left 

 nothing to be desired. If these or any similar ones 

 are still being issued, we shall, on behalf of our 

 readers, be glad to hear of them. 



Colour-Reaction. — Nylander was one of the 

 first to call the attention of biologists to the value 

 of colour-reaction in the study of the lichens. The 

 three principal re-agents used by microscopists are, 

 (1) iodine to give blue reactions ; (2) hypochlorite 

 of lime to give red reactions, and (3) hydrate of 

 potash to give yellow reactions. Iodine possesses 

 the property of turning starch and amyloid bodies 

 blue, and so is generally applied to sections of the 

 apothecia. when the asci are transformed from 

 their plain semi-transparency to a delicate blue, 

 thus rendering them at once visible, and their 

 forms and positions may be easily ascertained. 

 The lime and potash tests are generally used on 

 the thallus or leaf-like portion of the lichen, some- 

 times on the surface only, and at others on the 

 medullary layer. 



Mounting Medium. — The following method of 

 making an adhesive material for labels on glass, or 

 for fastening opaque objects for the microscope, is 

 given in the current number of the "Journal of the 

 Microscopical Society." Take 120 grains of gum 

 arabic and dissolve it in a quarter of a litre of 

 water. Dissolve thirty grains of powdered gum 

 tragacanth in a similar quantity of water. After a 

 few hours, shake the latter solution until it froths, 

 and mix with the former. Strain the mixture 

 through linen, and afterwards add to it 150 grams 

 of glycerine, previously mixed with i\ grams of oil 

 of thyme. 



Life-History of the Flea. — Professor Duncan. 

 F.R.S., gives us some interesting details bearing on 

 the life-history of that troublesome, though, to the 



