112 



SCIENCE-GOSSIP. 



Exchanging Fossils.— Collectors of scientific 

 objects might do far more by exchanging their 

 duplicates than is done. Every geological collector 

 has, or should have, very many duplicates of the 

 specimens mounted in his cabinet, any or all of 

 which would be prized by other collectors, who, 

 having duplicates also, would gladly exchange them 

 for species different from their own, a new or dif- 

 ferent form being always much more valuable than 

 a second specimen of those already mounted. More- 

 over, we are too much disposed to give up the 

 examination of formations, or beds from which we 

 have procured all the available fossils ; but if the 

 system of exchange was properly carried out, it would 

 be an encouragement to work on at beds supposed 

 to be already thoroughly examined ; for if we can 

 calculate upon thus disposing of all the fossils we 

 find for species from other formations, the more 

 duplicates we accumulate the better, and we, be- 

 coming better acquainted with the formations within 

 our reach, are the more likely to find uncommon 

 or rare forms not always to be procured by hasty 

 examinations. It would be well, therefore, if the 

 readers of S. G. would collect all the duplicate 

 fossils they can from their respective localities, 

 and make out a list of them for the use of 

 those with whom they wish to exchange ; then, by 

 first exchanging lists, both parties can select the 

 species they respectively require, and thus secure 

 the greatest variety of species, without the trans- 

 mission of unnecessary specimens. The character- 

 istic fossils of formations so frequently vary with 

 the locality, the name of the formation from which 

 specimens may be had furnishes no index as to the 

 species available. The suggested list, however, 

 meets the difficulty, and will enable collectors on 

 similar formations to exchange forms from each not 

 common to the two. I shall be happy to forward 

 a list of specimens from this locality to any collector 

 willing to exchange with me. — W. Gray, Mount 

 Charles, Belfast. 



MICROSCOPY. 



Substitute fob Clips. — I have adopted a plan 

 for the last three or four years, which answers all 

 the purposes of a "clip," for pressing down the 

 thin cover on a slide, and at the same time getting 

 rid of superfluous balsam. It consists in painting 

 the edge of the thin glass and the adjoining portion 

 of the slide with tolerably thick gum arabic. As 

 the moisture evaporates, the gum itself contracts, 

 thereby pressing down the cover, but so gradually, 

 that not the slightest injury is done to the most 

 delicate object. At the same time all superfluous 

 balsam is forced out at some weak point in the gum, 

 and can be easily removed, as it forms a small 

 globular mass. Of course there is not the slightest 



[May ], 1866. 



fear of the gum forcing its way into the balsam, 

 there not being the remotest affinity between the 

 two. In a day or so the gum can be removed by a 

 wetted handkerchief ; indeed the greater part chips 

 off of itself when thoroughly dry. Judging from 

 my own experience, I prefer this method to either 

 clips or weights. It answers as well for cells as for 

 the plane slide.— W. W. Spicer. 



Insect Scales. — At vol. ii. p. 29, % ninth line 

 from top of left-haud column, read hues instead of 

 lines ; and as the scale figured on page 58 is from 

 the small garden white or " cabbage " butterfly, the 

 name should be P. Rapte instead of P. Brassicce. 

 The scales of the latter differ chiefly in being more 

 elongated than those of the former insect. Since 

 making the notes on the subject, another scale 

 which I have never seen figured, has turned up, and 

 deserves to have had a place in the chapter. I do not 

 know whether to refer it to a Leptocircus or to a 

 Morpho, in which genus considerable latitude for 

 variety is suspected. Pieces only of the wings came 

 into my possession, and I did not take the necessary 

 precautions to insure accuracy in time. By re- 

 flected light the objects in question are brilliant 

 green and blue respectively ; by transmitted light 

 they are crimson-lake shading into purple and 

 yellow, and exhibit beaded markings. The Micro- 

 graphic Dictionary gives interesting figures of the 

 scales from Lasiocampa Quercus and from the larva 

 of Attacjenus Pellio. I recommend the examination 

 of scales from the Burnet moth the orange-tip 

 butterfly, white plume moth (hair-like scales), and 

 various other Lepidoptera and Curculionidse. In my 

 figure of the scales of the Pencil-tail (Science 

 Gossip, vol. i. p. 230), I have not done anything 

 like justice to their beauty. The best specimens 

 lie across the back of the creature. I prefer the 

 scales of insects " mounted dry." — S. J. M'Intire. 



Toxonidea. — With the exception of vol. vi., New 

 Series of the Quarterly Journal of Microscopical 

 Science, and Pritchard's "Infusoria," I do not know 

 of any work in which specimens of the beautiful genus 

 Toxonidea are figured, and the Editor of Science 

 Gossip has done good service to all who are inter- 

 ested in the study of Diatomacea;, by introducing to 

 his numerous readers so admirable an illustration of 

 the finest species of the genus as that figured on 

 page S7. There are three species of the genus 

 Toxonidea ; viz., Toxonidea Gregoriana, T. insig?iis 

 and T. undulata. The two former are found on the 

 Northumberland coast, the first rather sparely, and 

 the second in great abundance. Tox. undulata has 

 been obtained by Mr. Norman, of Hull, from the 

 stomachs of ascidians taken from deep water off the 

 coast of Hull. With the exception of Northumber- 

 land, I have only heard of two places in which 

 Toxonidea have been found on the open sea-coast, 

 once in Dublin Bay by the Rev. E. O'Meara, in 



