110 



HARDWICKE'S SCIENCE-GOSSIP. 



we fiud beautiful and couspicuous flowers. The 

 nectar-seeking lepidoptera carry the pollen from 

 flower to flower, and thus insure cross fertilization ; 

 hence conspicuous and beautiful flowers are bene- 

 ficial to the plants, and would assuredly arise iu the 

 course of time. Moths are the chief, if not the 

 only agents by which tlie fertilization of most 

 orchids is attained. 



Passing from the lepidoptera to the diptera, or 

 two-winged flies, we find another very remarkable 

 modification of the mouth-organs, and it is amongst 

 these insects that microscopists seek and find 

 some of the most interesting and beautiful objects, 

 which are favourites with those who only use the 

 microscope as an amusing toy, owing to their 

 curious forms and delicate structure. 



In the mouth of the adult dipterous insect the 

 labium is again enormously developed, but it is 

 prolonged, together with the anterior parts of the 

 head, into a kind of trunk or proboscis, and this 

 folds on itself with a knee-like joint. 



The terminal portion of this proboscis consists 

 almost entirely of a large fleshy labium, grooved 

 above, and closed as far as the extremity of the 

 groove by a long narrow labrum, or upper lip. The 

 extremity of tlie labium beyond the groove forms a 

 pair of more or less developed lobes, united 

 behind, and capable of being used as a sucker (figs. 

 79 and 81). Thete suctorial lobes difi'er exceedingly 

 iu structure and magnitude in different diptera. 

 In the house-fly and its allies they are simple, and 

 folded together like a closed book when at rest; 

 but in the bloodthirsty gadflies they are so large 

 that they are rolled up when not in use (fig. 79). 



The mouth of the gadfly will serve as au excellent 

 starting-point in the study of the dipterous mouth. 

 The numerous lancets seen iu the fig. 79, when at 

 rest, lie in the groove of the labium, and are pro- 

 tected by the great scale-like maxillary palpi, |;. 

 The lancets are, first, the outer lobes of the great 

 maxiUse msd , closely similar to the same parts in 

 the mouth of the bee; secondly, a pair of sharp- 

 pointed curved organs, md, rough on the surface 

 like a minute rasp, and finely-toothed at their edges 

 (fig. 80); these probably represent the labial palpi, but, 

 according to some, are modified mandibles ; lastly, 

 the sharp labium and the fine and equally sharp 

 ligula,— in all, six in number, a formidable and 

 much-dreaded arsenal of small arms. The eflicacy 

 of the labial palpi as organs of offence may be 

 easily judged by examining their rasp-like extre- 

 mities with a quarter-inch objective (fig. 80). 



( To be continued?^ 



" We must entirely dismiss the conception that 

 mere anatomy by itself can have any decisive bear- 

 ing on the question as to man's nature and being as 

 a whole."— Mivart's 31an and Apes. 



MICROSCOPY. 



MouNTiXG Mosses, &c.— I cannot veuiure to 

 say what may be the " best" way to mount leaves 

 of mosses, &c., but I have found mounting them in 

 fluid quite satisfactory, and have specimens mounted 

 about eighteen or twenty years ago in perfect 

 order. The cell consists of a ring of Brunswick 

 black formed on a Shadbolt's turntable. It must 

 be made sufficiently deep. The fluid is then dropped 

 iu, the object and cover adjusted, superfluous 

 moisture drawn off with blotting-paper till the cover 

 sticks by suction. The slide is then carefully 

 adjusted on tlie turntable, and sealed in with as little 

 Brunswick black as will cover the junction of cover 

 and cell. This sealing must be closely examined 

 all round and made perfect. "When this is dry, it 

 should be repeated till a firm smooth ring covers 

 more than the edge of the cover, and at least half 

 of the projecting wall of the cell. A skilful operator 

 will seal in objects in one process, or two at the 

 most ; but this requires experience as to the con- 

 sistency of the Brunswick black, &c. The cell 

 must be perfectly level (as it will be if the black is 

 fluid enough and clean), and the cover should reach 

 to about half the width of the cell-ring. If I re- 

 member rightly, I used indifferently for fluid, proof 

 spirit TO) distilled water f^ (even vpeaker) ; naphtha 

 and water ; acetic acid and water — both very weak 

 and mixed by guess. 1 strongly suspect that the 

 proportion signifies little if the mixture is but weak 

 enough. TetrapJus pellucida thus mounted, the 

 whole plant, root, gemma;, and all, is a most beauti- 

 ful object ; but it mounts well iu balsam if carefully 

 dried, and in this retains its lovely colour, which is 

 lost iu fluid. Sphagnum-leaves mount well in fluid. 

 Many mosses mount well in balsam, if carefully 

 dried first. Coaguline was not used in my day, and 

 I do not know it.— ii. F. S. 



Query about Microscopes. — The mechanical 

 stage is much superior to any other form of stage, 

 but it makes a somewliat heavy addition to the cost 

 of the microscope. It is almost indispensable when 

 the higher objectives are used, viz., from an k up- 

 wards. The next best would be either the sliding 

 and rotating or the lever-stage; with careful manipu- 

 lation an I can be used with either form. A good 

 working instrument can be had without a mechan- 

 ical stage, whicii can be added at any future tiuie. 

 The cost of a really useful stand, to which additions 

 could be made froai time to time, would be (if 

 monocular) about £6. 15s. without mechanical stage, 

 which would entail an additional cost of £2. A 

 bmocular, with circular rotating stage and rack- 

 adjustment to eye-pieces, would cost about £7. 10s. 

 With respect to objectives, it is always desirable to 

 have the best, if the cost is no object ; but where it 

 is, Guudlach's objectives are generally very good. 



