HARD WI CKE 'S S C/jEJV CE-G OSSIP. 



159 



at the fire before applying the asphalt, so as to make 

 it bite the fronds of the polyzoa more keenly. Never 

 let gum or any other mucilage touch the fronds that 

 are to be treated by the asphalt process, as these 

 interfere with the adherence very much. The asphalt 

 I use is the common sort, free from sand, employed 

 in the constmction of pavements for our streets. 

 When a specimen of polyzoa is wished to be operated 

 upon, let it be heated as above directed, then lay it 

 down flat, and with a piece of iron heated nearly to 

 redness (the kitchen poker does very well), melt a layer 

 of the asphalt over the surface of the frond, spreading 

 it evenly with the iron. Let there be a bit of tough 

 brown paper ready beside you to cover the surface of 

 the asphalt, and while it is still hot, press the paper 

 down over the surface evenly with the fingers. The 

 layer of tough paper strengthens the asphalt very 

 much, and afterwards, when the specimen is finished, 

 the paper adheres more firmly to the tablet on which 

 it is mounted than wlien the asphalt is used alone. 

 When I lift large fronds of polyzoa from the shale, I 

 use, first a layer of the asphalt ; next, a layer of 

 paper ; then a second layer of asphalt and paper. 

 This method forms a firm thin cake, which, in large 

 specimens, is less liable to break across. The next 

 operation, after fixing the asphalt to the fronds of the 

 polyzoa, is to place the specimens in water, and let 

 them lie until the shale softens. The length of time 

 this requires varies according to the nature of the 

 shale. In some cases the polyzoa parts from the 

 shale in a few minutes, in others it may take as long as 

 an hour or two, or even a day ; but the process may 

 be hastened by placing the specimens in a saucer filled 

 with water, and as the shale is softened keep picking 

 it away with a thin sharp knife imtil you see the 

 fi-onds of the polyzoa appearing ; then with a worn 

 nail- or tooth-brush mash the surfaces of the speci- 

 mens until you consider you have got them quite 

 clean, and the cell-pores well exposed. If the fronds 

 of the polyzoa have been well fixed to the asphalt, 

 you may use the greatest freedom in the mashing of 

 the specimens without fear of their removal by the 

 brush. My collection contains a large series of beau- 

 tiful specimens that I have treated according to the 

 above method, and I find no difficulty in lifting the 

 largest fronds of Fenestella and other fenestrate genera 

 of polyzoa that are preserved in our shales, so as to 

 show their poriferous face. Lately I have managed to 

 show by the same process the poriferous face of some 

 of the feathery fronds of the more delicate branching 

 Glaiicononie with perfect success. The last thing I 

 have to note regaixling this process is, that the surplus 

 asphalt and paper can easily be neatly cut away from 

 around the fronds by using a pair of sharp scissors. 

 For cleaning small specimens of polyzoa that are 

 intended for microscopic examination, I use the fol- 

 lowing method. After having picked the specimens 

 out from amongst Ae weathered limestone shales, 

 where they often have a thin layer of clay adhering 



I to them, I take a glass slide snd cover it with a layer 

 j of thin gum. I then, with the forceps, lift all the 

 j fragments of polyzoa that I wish to clean, and place 

 ' them on the slide with the poriferous face uppermost 

 aferwards allowing the slide to diy slowly for a day 

 or two. When the gum is quite hard, place the slide 

 in a saucer of water, and brush the specimens gently 

 and quickly with a nail- or tooth-brush. The gum 

 will hold the fragments of polyzoa firmly and safely 

 in position, quite long enough before dissolving, so as 

 to allow of the specimens being well cleaned. When 

 this is done, 'allow the slide to lie in the water until 

 all the specimens are melted off from the surface : 

 they can afterwards be collected with a soft hair- 

 pencil, and dried on blotting-paper, when they are 

 then quite ready for mounting. By this method, t he 

 appearance of the polyzoa is veiy much improved, 

 and the cell-pores much more satisfactorily examined. 



John Young. 

 Httntcrian Rlitsciini, University of Glasgozo. 



MICROSCOPY. 



The Quekett Microscopical Club. — We have 

 received No. 32 of the Journal of this energetic and 

 popular society, iDublished by Hardwicke & Bogue, 

 192, Piccadilly. It contains well-illustrated papers, 

 by W. K. Bridgman, on the ' ' Principles of Illumi- 

 nation in connection with Polarization"; by Prof. 11. 

 L. Smith, " On a New Method of Mounting Micro- 

 scopic Objects" ; by Dr. Francis E. Hoggan, " On 

 a New Process of Histological Staining " ; and by 

 James Fullagar, on " Ttibicolaria Najas." In ad- 

 dition to the above, we have also the Annual Address 

 of the President, Dr. John Mathews. 



Mounting in Damar. — I am glad to see by the 

 Science-Gossip for May, that some one as well as 

 myself has used heat in the process of mounting in 

 damar, and I hope with as satisfactory results as 

 I have obtained. I observe in "J. A. Le M. H.'s" 

 article on the subject that he asks two questions which 

 I trust I can answer to his satisfaction, ist. " How 

 air-bubbles are to be prevented from forming within 

 an object when upon a hot slide without any 

 medium ? " When air is heated it is rarefied ; there- 

 fore there would be less air between the slide and the 

 glass cover, when slightly heated than when quite 

 cold. The only reason I have for heating it first is, 

 that it facilitates the damar running in by capillary 

 attraction, which, as it ran in, would drive out 

 what air there was. Of course I do not heat 

 the object long enougli to dry up the turpen- 

 tine or benzole in which it had previously been 

 soaked. . The only time I have any trouble with air- 

 bubbles is when, by accident, I heat the medium to 

 boiling pitch ; which I now avoid by the following 

 slight alteration of my process. Instead of having 

 the flame of the spirit-lamp about two inches below 



