HARDWICKE'S SCIENCE-GOSSIP. 



187 



phanerogamic as well as cryptogamic plants for a 

 long time past, and find them all that can be desired. 

 — John E. Vize, Forden Vicarage, Welshpool. 



Handy Block for Work-Table. — Mr. W. J. 

 Simmons's sketch of a "Handy Block for the Work- 

 Table " has induced me to send you a sketch of one 

 I have used for a long time, and found to answer 

 well for dissecting purposes. It is easily made, very 

 portable, and could be manufactured out of an old 

 cigar box ; and from the sketch will need very little 



Fig. 107. 



explanation. It is made of pine about % of an inch 

 in thickness, with a small drawer at the back to hold 

 all necessary dissecting instruments, brushes, watch- 

 glasses, knives, &c. A piece of glass is fitted in the 

 top on which the watch-glass or glass trough is placed 

 for working purposes. For a lens I use one on a 

 brass stand, such as is used for botanical purposes. 

 For a mirror I have a piece of an old looking-glass, 

 cut to size, and put in a slanting position so as to 

 reflect the rays of the lamp up through the watch- 

 glass.— J. Boggiest. 



ZOOLOGY. 



Snow Bunting in Worcestershire. — All doubt 

 as to the ownership of the eggs was settled by my 

 nearly catching the bird on the nest, as she was 

 sitting at the time. I am well aware of its rarity, but 

 knew at once the prize I had secured. — D. W. B. 



Caterpillars and Change of Food. — Two or 

 three years ago, I got from a dealer about a dozen 

 caterpillars of C. elpenor (the elephant hawk- 

 moth), which had been fed on vine leaves. As it 

 was more convenient to get the food natural to the cater- 

 pillar in this country (the common willow herb), I tried 

 them with that plant, but they absolutely refused to 

 touch it, and at some inconvenience I had to procure 

 them vine leaves which they at once greedily ate. I 

 was very much puzzled at the time to account for this 

 refusal of larvae to eat their natural food, but I think 

 I have lately obtained a clue to the mystery, for 

 Professor Weismann, in his "Studies in the Theory of 

 Descent," states that there are three other species of 



this genus (Achemon, Cretica and Capensis) found as 

 far apart as N. America, India, and the Cape, all of 

 which are vine feeders. This looks as if the common 

 ancestor of all the species must have fed on the vine, 

 and that when Elpenor or its predecessors reached 

 this country it was compelled either to adopt another 

 food plant or suffer extinction. It is of course very 

 surprising that my caterpillars should have 

 instinctively preferred what was probably the 

 natural food of the genus to that food which the 

 species must have fed on for such vast periods of 

 time, but after all it is not more surprising 

 than the appearance at the present day, in 

 some animals, of limbs and muscles that 

 have been functionless for equally long 

 periods. — R. B. P., Eastbourne. 



Aphides on Rose Trees. — This season 

 the rose-bushes in south-western Essex are 

 dreadfully infested with the green aphis and 

 the small leaf-rolling caterpillars which have 

 almost totally destroyed what would have 

 been otherwise a plentiful show of roses. At 

 the same time the wild roses in the hedge- 

 rows and in Epping Forest are quite clear. 

 Is this immunity of the wild species a general fact, 

 and if so, what is the reason ? — J. W. Slater. 



Butterflies' Eggs, &c. — It maybe interesting to 

 some of those who read the article under the above 

 title, on page 115 of the present vol. of Science- 

 Gossip, to know that temperature is nofrthe only cause 

 of variation in the colour of butterflies. M. Nicolas 

 Wagner, by a series of experiments displayed before 

 the Academy of Sciences, about the year 1865, 

 showed that electricity also produced this effect. 

 His experiments were performed on Vanessa urtica. 

 He found that electric currents changed reds into 

 orange, and blacks into reds, and with a constant 

 battery, a weak current produced spots varying in 

 shape with the strength of the current. He further 

 demonstrated that the colours naturally existing in 

 the butterfly's wings were due to currents in that 

 organ, the most powerful of which passes from 

 the attachment of the wing outwards along the 

 middle nervure to the outer edge. In these experi- 

 ments he used a Bois-Raymond galvanometer of 

 20,000 coils. The following are the conclusions he 

 arrived at. I. The existence of fixed electric currents 

 in the wings of insects. 2. The possibility by means 

 of electric currents to provoke a change in the shade 

 and disposition of the colouring matter. 3. And the 

 possibility, by means of these currents, to produce a 

 kind of atrophy and to change the shape of the wings. 

 He concludes as follows : " with these facts as basis, 

 I propose to pursue my research on this subject." — 

 R.J.S. Wood, Q.C.C. 



The Sand Grouse still in Suffolk.— I am 

 pleased to inform you on reliable authority that the 



