HARDWICKE'S SCIENCE-GOSSIP. 



37 



autumn, a few resting-spores of the Volvociiiecc, but 

 to which species they belonged I beheve it impossible 

 to decide, save by watching their development. I 

 have never seen the orange-coloured resting-spores— 

 the results of conjugation— which were described by 

 the recently deceased'Ehrenberg as distinct forms 

 under the names V. aitrcns and ]\ stdlatits. Each 

 has a thick double envelope and bright orange- 

 coloured central mass, the latter being covered with 

 spines. I found I could demonstrate the cilia by 

 oblique illumination almost as well as by iodine 

 staining. I should be very glad to learn from some 

 of your correspondents how best to preserve Volvo- 

 cinea. "A thing of beauty is a joy for ever," but the 

 joy in my case is confined to sweet memory. Calcic 

 chloride and glycerine very much alter the gonidia, 

 though the temporary action of these reagents renders 

 evident (or forms de novol) the double lines connect- 

 ing the gonidia. Though the multiple nature of 

 Volvox has been clearly proved, yet a correlation — a 

 sympathy — of even the proximate cause of which we 

 are entirely ignorant — a sympathy whose analogue we 

 see in all Nature — is observable in the identity of the 

 direction in which the pairs of cilia on the gonidia 

 move, no less than in the carrying out of the principle 

 of the division of labour, by which some of the gonidia 

 take on the sexual function, some producing sperma- 

 tozoa, others germ-cells, whilst the rest undergo no 

 change, but continue the nutritive process. — David 

 A. King. 



Forms of Heliopelta.- — In looking over some 

 unprepared diatomaceous earth (Nottingham deposit) 

 I found a complete double frustule of Heliopelta, which 

 I singled out and proceeded to clean under a micros- 

 cope on a glass slide by itself. After a little manipu- 

 lation with a very small camel-hair brush, wetted, I 

 succeeded in splitting the frustule in the middle, and 

 saw with suri^rise what I had not remarked previously, 

 that the five sides had a different number of rays and 

 septa. One had four rays (Maltese cross) called in 

 the Micrographic Dictionary H. Leeiiwenhockii, and 

 the other with five rays and septa. Have any of your 

 readers come across a similar abnormal (?) form ? In 

 the Micro. Diet. I see there is a query about the fnis- 

 tule being single. The form I found was undoubtedly 

 a double frustule. I find that authorities differ as 

 regards the names of the various Heliopelta ; some say 

 that H. Metii has four rays and septa, whereas the 

 Micro. Diet, terms it //. Leeiiwenhockii. Which is 

 correct? — G. M. Gowan. 



Fluid Cavities in Crystals. — At a recent 

 meeting of the Chemical Society, Prof. W. N. Hartley 

 made a communication entitled "A Further Study of 

 Fluid Cavities," in which he described the results of 

 his examination of a large number of topaz and of 

 rock sections, mostly granites and porphyries. The 

 fluid contained in the cavities was almost invariably 

 water, but it was very remarkable that the cavities 



often took the form of the crystals in which they were 

 contained, and nearly always arranged themselves 

 symmetrically with regard to the faces of the crystal. 



Diatoms, &c. — I have some beautiful gatherings 

 of Diatomacece in situ, on marine algK, &c., and 

 shall be happy to correspond with persons interested 

 in their study. I find a very good way for preserving 

 them is, to dry the algre on the slide, and, when 

 ready for balsam, to drop on some pure benzole first, 

 which will remove the endochrome from the valves, 

 and replace the air they contain. This discoloured 

 benzole can be soaked out by blotting-paper, and the 

 balsam laid on as usual. I find the best medium is 

 balsam diluted with benzole, which can be applied 

 without heat, as air-bubbles give very little annoyance 

 with this medium, Walter White, of Litcham, sells 

 tubes of "damar" which can be used in the same 

 way with very satisfactoiy results ; and in many cases 

 there is nothing gives such satisfaction, and certainly 

 I know nothing so easily worked, and have algas, 

 now in it for four years, as perfect and beautiful as 

 the first day. There is not the least change, and 

 their natural colour is as bright and lovely as when 

 in their native element. I also find "damar" a 

 capital medium for mounting scale-mosses, &c. — T. 

 3IeGan7i, Burren, Ireland. 



How to filter Water to obtain Minute 

 Organisms. — Dr. A. Meade Edwards writes as 

 follows to the Ar/ierican yournal of LTicroscopy : — 

 "I can tell you of two good ways of accomplishing the 

 above object ; both of which have their applications 

 under special circumstances, and both of which I have 

 used for several years with great satisfaction. First, 

 a modification of the conical muslin bag. Have a 

 conical muslin bag, but leave the point open, and place 

 therein a one-ounce wide-mouthed phial, which fasten 

 by means of string tied around its neck, or, better 

 still, with a rubber ring. Now pour your water into 

 it to any extent. The water will run through the 

 meshes of the muslin, and the minute organisms will 

 gradually collect in the phial below. When you have 

 enough, remove the phial, turn the bag inside out and 

 wash it thoroughly in clear water, replace the phial 

 by another, and you are ready for another haul. 

 Such a bag having a stick tied across its mouth, and 

 a large cork fixed to the phial, can be towed after a 

 boat or ship, and the ' wonders of the deep ' 

 gathered in any quantity. My second device I have 

 commonly made use of in examining potable water ; 

 and I have the sediments so collected from several of 

 our large cities. Anon it is my intention to publish 

 something with regard to what I have therein. Take 

 a large glass jar of a half to one gallon capacity — a 

 large beaker or 'specie jar' will do, or even a pitcher 

 may be used on a pinch ; fill it with the water we 

 wish to ' concentrate ' at night, and let it stand. 

 Next morning carefully pour off all the water except 

 about a pint. Fill up again, and let it stand until 



