SCIENCE-GOSSIP 



257 



readers through the British species on to a study 

 1 if the wider field of the butterflies of the world. 

 In selecting the material for the new plates to 

 illustrate his work, the author has chosen figures 

 chiefly representing recently-described and hitherto 

 unfigured species. The introduction is a useful 

 piece of writing, which will easily and pleasantly 

 help many coming students over the initiatory 

 scientific drudgery, which so many " butterfly- 

 catchers " sadly shirk, leaving themselves always 

 in the category of collectors. We consider this 

 work an instalment of what bids fair to be one of 

 the most important, recently published for the 

 guidance of the British entomologist. — [J. T. C] 



An Introduction to the Study of the Diatomacea;. By 

 Frederick Wm. Mills, F.R.M.S., with a Biblio- 

 graphy by Julien Deby, F.R.M.S. pp. xi. and 

 243, large 8vo, with some illustrations. (London : 

 Iliffe and Son. Washington : The Microscopical 

 Publishing Co. 1893.) Price 12s. net. 



This useful introduction will be found valuable to 

 the students of diatoms, as may be supposed from 

 some of the headings of the ten chapters into which 

 the work is divided, such as Structure, Movement, 

 Classification, Reproduction, Collecting, Mounting, 

 and How to Photograph Diatoms. The illustrations 

 are hardly what we might expect, as they are con- 

 fined to microscopes and apparatus used in the study 

 of these organisms. The introduction proper only 

 occupies seventy-seven pages and the bibliography 

 183 pages. This is the most important part of the 

 book, and seems to have been prepared with con- 

 siderable care. It would have been additionally- 

 useful if Mr. Mills had given the limit of date of 

 Mr. Deby's compilation, as much of it refers to 

 papers in various scientific magazines. The preface 

 is dated April, 1893 ; but those interested in later 

 search will not know where they are to take it up 

 for more recent literary material. — [J. T. C] 



Farm Vermin, Helpful and Hurtful. By various 

 writers. Edited by John Watson, F.L.S. 85 pp, 

 8vo, illustrated. (London and New York : 

 William Rider and Son, Limited.) Price 2s. 6d. 



This is No. 6 of " Rider's Technical Handbooks," 

 and we think it too highly priced for those whom it 

 is intended to benefit, considering how little 

 novel matter it contains. The dozen illustrations 

 are, as a rule, crude and inartistic, being of small 

 use to those who live on farms. We do not see the 

 advantage of giving pictures of such well-known 

 " vermin " as a fox, a rabbit, squirrel or hedgehog 

 for the guidance of our farmers. 



Ponds and Rock Pools, with Hints on the Collecting 

 for and the Management of the Micro-Aquarium. By 

 Henry Scherren. 208 pp. 8vo and 66 figures. 

 (London : Religious Tract Society, 1894.) Price 

 2S. 6d. 



Although much has been written in many books 

 upon this subject there was still room for such a 

 popularly written book on micro-aquatic animals. 

 This is eminently a beginner's guide, and the com- 

 mittee of the society which has published it will, 

 doubtless, be rewarded by having created many 

 new workers in this field. Founded on articles 

 which Mr. Scherren wrote for the " Leisure Hour," 

 the chapters of the book before us have been much 

 added to and largely redressed. The figures will 

 be enticing to the tyro who does not know how to 

 begin collecting aquatic microscopic objects, and 

 will materially assist his first efforts in that 

 fascinating pursuit. It makes a handy and useful 

 manual. 



The well-known firm of R. and J. Beck, of 68 

 Cornhill, London, issue free to microscopists, their 

 new illustrated catalogue of microscopes, object 

 glasses and apparatus, just published. Being 

 nicely bound and profusely illustrated, it hardly 

 ranks with the ordinary trade catalogue, but forms 

 a useful dictionary, brought up to date of publica- 

 tion, of instruments used in microscopy. 



Microscopic Preparations. — We have received 

 from Mr. Ernest Hinton, 12, Vorley Road, Upper 

 Holloway, London, two preparations for examina- 

 tion. The first is Volvox globator, showing the 

 beautiful golden resting spores. It is a very 

 striking object when shown with paraboloid. The 

 other is a leaf of the carnivorous plant Drosera 

 rotundifolia, showing captive insect being held down 

 by the glandular hairs. It would be a good subject 

 for photography on account of its pleasing colour. 



Selecting Test Diatoms. — Can any reader ot 

 Science-Gossip inform me how Moller and other 

 "professionals" arrange the " test " diatomaceae in 

 groups. In most cases it is easy when diatoms 

 have been dried on a slide to pick them off with a 

 hair, or a fine thread of spun glass, and as a matter 

 of pure preference I use glass. This plan answers 

 fairly well even with such delicate species as 

 Grammatophora marina, and the larger Pleurosigmas ; 

 P. attenuatum and P. balticum to wit, may be safely 

 picked off a slide, provided that they were well 

 washed in distilled water before spreading, and 

 that they have not been left too long on the slide 

 after drying. Any attempt, however, to remove 

 P. angueatum, Surirclla gemma or Navicula rhomboides 

 from the slide generally results in the destruction 

 of the diatom, and to my annoyance I smashed up 

 the only specimen of a fine Asteromphalus from a 

 Mediterranean gathering, in trying to select it 

 Such species are therefore too delicate and fragile 

 to be selected after the material has been dried. 

 In a letter I received some years ago from M. 

 Tempere, the well-known diatomist, in reply to a 

 question on this subject, he said, "To select the 

 smaller Plcurosigma you must place on the cover 

 a drop of distilled water containing a few valves, 

 when the water is nearly evaporated you will find 

 it an easy task to move and arrange the diatoms as 

 you wish, taking out the extra ones. Allow to dry. 

 and mount as usual ; Plcurosigma are better mounted 

 dry, should you require them in balsam add a little 

 gum to the water." This cannot, however, be the 

 plan used in mounting the " Typen platten " where 

 a number of different species have to be picked out 

 of different gatherings, for there must be some way 

 of transferring them from one cover to another to 

 get them all together. I can scarcely suppose that 

 this method is a " trade secret," for life is far too 

 short and eyesight too valuable for any ordinary 

 mounter to attempt to emulate Moller. It would 

 be useful to be able to select these delicate diatoms 

 when they happen to be found on a slide on which 

 the material has alreadv been dried. — G. H. Bryan 



