100 



THE AMEKICAN MONTHLY. 



[May. 



the board over so that the glass shall be 

 at the bottom, I have a little cell with a 

 glass floor. With the aid of a piece of 

 paper gummed to the wings, I introduce 

 a fly into this cavity in such a manner 

 that the pulvilli shall rest upon the floor. 

 Then, putting the board under the micro- 

 scope with the glass slide uppermost, we 

 have the fly's feet under our eyes. The 

 insect, struggling for liberty, places his 

 pulvilli against the glass, and leaves after 

 each effort traces that may be observed 

 very distinctly, for they are perfectly visi- 

 ble in a good light. 



' We may discover, whenever the feet of 

 the fly come again into contact with these 

 tracks or minute drops, that they are com- 

 posed of a very liquid substance, for they 

 spread quite readily on the glass. We 

 cannot admit, as some naturalists assume, 

 that the liquid can hold the club-shaped 

 hair-ends by suction. If this were the 

 case, the ends would change shape during 

 the suction, and would take the form of a 

 disk. The fly puts its feet down and lifts 

 them up with an incomparable facility that 

 would not exist if the limb were really 

 acted upon by the pressure of the air.' 



— The first editions of the catalogues of 

 W. H. Walmsley & Co., embracing tele- 

 scopes, spectacles, eye-glasses, and photo- 

 graphic cameras, lenses, etc., in three parts, 

 have just come to hand, together with the 

 fourteenth edition of the catalogue of mi- 

 croscopes and accessories of R. & J. Beck, 

 which is issued by the same firm. All of 

 these catalogues are carefully prepared, 

 and a credit to the establishment. Among 

 many excellent articles to be found in them 

 we notice a developer for photographic 

 plates which Mr. Walmsley has prepared 

 and which he states to be the ' best and 

 most economical developer in use.' This 

 will doubtless be highly esteemed by those 

 who apply photomicrography in their 

 work. There is also a ' list of reagents for 

 microscopic staining,' with directions for 

 using them. All the forms of Beck's mi- 

 croscopes and accessories are figured in 

 the catalogue, and in addition some of 

 the stands made by the Bausch & Lomb 

 optical company. We notice, also, that 

 the labels for slides devised by Mr. I. C. 

 Thompson, of Liverpool, are offered for 

 sale in sets of a thousand. 



— Mr. William Wales has changed his 

 place of business in New-York, and will 

 hereafter be more easily found by those 

 who visit the city. He is now at 53 Nas- 

 sau street, where he will keep on hand a 

 full assortment of microscopes, accessories. 



and objectives. We are pleased to learn 

 that he has moved down town, and doubt 

 not the change will be to his advantage. 



CORRESPONDENCE. 



Mailing Packages of Diatoms. 



To THE Editor : — I have been much 

 interested in the past in practical articles 

 on mounting. Wish there might be some- 

 thing on preparing fluid mounts. Have 

 gained many valuable suggestions from 

 the Journal as to the minutiae of mount- 

 ing. 



Can you tell me, through the Journal, 

 how one can send small exchanges to 

 foreign countries ? There seems no limit 

 to the vials of fluid as diatoms which one 

 may receive from them. I have received 

 as many as 20 vials in one box, but if 1 

 send one vial containing a few drops, even 

 in a tightly corked wooden flask, it is re- 

 turned to me from the New York post 

 office stamped ' liable to injure and deface 

 the mails.' 



M. A. Booth. 



[The only way to send specimens of 

 diatoms in fluid abroad is to put letter 

 postage on them. Abroad, post offices 

 are established for the convenience of the 

 people, to encourage intercommunication, 

 and in Holland one can send butter, her- 

 rings, and perishable merchandise by 

 mail, and even have the bills collected 

 and the amounts returned for a trifling 

 fee. 



Let some one put a dried herring in the 

 New-York post office, and see how far it 

 would go I Our postal laws are absurd in 

 many respects, but they would not be so 

 bad if the officials saw fit to use discretion 

 in interpreting them, instead of acting like 

 automata. — Ed.] 



Exchanges. 



Exchanges are inserted in this column without charge, 

 [They will be strictly limited to mounted objects, and 

 material for mounting.] 



Will exchange well mounted slides for others well 

 mounted. 



H. H. PEASE, 

 1271 Broadway, N. V. 



Living red Astasia natnatodes {Euglena viridis) 

 and Volvox sent on application, or mounts of the same 

 in exchange for algx, fungi, or infusoria. 



J. M. ADAMS, 

 Watertown, N. Y. 



Will exchange various mounts of crystals for other 

 slides, and material for mounting. 



JAMES E. WHITNEY, 



Rochester, N. Y. 



