June, 1908.] 



KNOWLEDGE 



141 



The catting-hook is a curved knife which can also be screwed 

 on to the collecting stick, and is intended for cutting roots or 

 water weeds ^vhich are otherwise out of reach. 



Tib. l.~a £■ = 9 in. ; angle at e = 140". 



The Fl.4T Bottle. — Can now be obtained from the optician?, 

 well made and cemented with fusible cement in the fire. When 

 first invented by the late Jlr. T. D. Hardy it was made by 

 cutting a LI shaped piece out of a thick flat piece of india- 

 rubber or similar material, 4 to .5 in. long by 2 to '2i in. wide, 

 and f to I in. thick : a .square of thin plate glass of same size, 

 cemented by means of Millers' caoutchouc cement on each 

 side, completed the bottle. A thick piece of indiarubber 

 if>, however, so expensive that it is cheaper to buy the finished 

 article. The flat bottle is used for searching over pondweeds 

 with the pocket lens at the side of the pond, or examining the 

 water which has been collected and condensed witli the net. In 

 round bottles it is very difficult to see minute animals clearly, 

 whilst a thin flat bottle allows the whole contents to be readily 

 scrutinized with a pocket lens of considerable power, and one 

 can thus at once determine whether it is worth while to take 

 home a sample from that particular pond for further e.xamina- 

 tion under the microscope. 



The Pocket Lens best adapted for field work is Zeiss' 

 improved aplanatic lens, magnifying 6 diameters, which has a 

 very large flat field, long focus, and the most perfect definition 

 all over the field. 



The various groups of plants and animals commonly designated 

 as Pond-life, which inhabit freshwater lakes, ponds and ditches, 

 consist of AlgiB, Desmids, Rhizopoda, lufu-^oria. Sponges, 

 Hydra=, Kotifera, Polyzoa, Cladocera or Water-fleas, Copepods, 

 Hydrachnida, Worms and Insect larvas. All these can be 

 divided for the purpose of collecting into two groups — the free- 

 swimming, and those that are usually atta:;hed to water plants 

 or submerged objects, and each of these grou])S must be 

 captured in different way.<. 



All free- swimming or floating forms, which collectively are 

 designated by the word " plankton," are best secured with the 

 net. The net is passed through the water two or three or more 

 times, and then held up ; the water will run out ju half a 

 minute, and quite at the last the condensed animals will be 

 seen entering the little bottle like a cloud, where they can be 

 subjected to a preliminary examination. It is best, however, 

 to empty the contents into the flat bottle, in which the examina- 

 tion with the ]iocket lens becomes very much easier, and most 

 of the forms one is acquainted with can be recognized at a 

 glance. In this way thousands of Algie, Infusoria, Rotifcrn, 

 Daphnia, &c., can be captured in a fc'W minutes if the pond be 

 a prolific one. Having thus ascertained that the dip contains 

 some desirable forms, the water is poured into a larger wide- 

 mouthed collecting VK>ttle, of which three to six should bo 

 carried in the bag. These bottles should be numbei'ed ; for it 

 is often advantageous to keep the water of different i)Onds 

 separate, so as to be able to know at home from which pond a 

 particular creature has come. Ponds vary exceedingly as regards 

 their contents in Pond-life ; a smiUl pond may bo very pro- 

 lific, whilst another, |iossibly a larger jiieco of water only a few 

 yards off, may contain hardly anything worth colhcting. By 

 trying all the difl'erent ponds, small and large, within reach of 

 an attornoon's walk, one usually suci-eeds in obtaining a good 

 gathering of free-swimming forms. The net quickly condensts 

 a large volume of water, so thit few species, even if present in 

 small numbers only, will escape being cajitured. Si^veral other 

 methods of cot dousing pond water have been devised, but the 

 collecting net with bottle attached is so simple and efl'ective 

 that we need not trouble about any other apparatus. It may 



be advisable to try the larger ponds in various places, and both 

 near the surface and also in deep water, as some plankton 

 forms may have collected in one particular comer of the pond 

 and be absent elsewhere ; this is often the case with Volvnx 

 r/lobator. The use of a boat on larger lakes is very desirable 

 when available. For Rotifers and other active free-8wimmers 

 it is not advisable to disturb the mud at the Vjottom of the 

 ])ond, but certain species of Cladocera, Hydrachnida, and insect 

 larvje can only be found at or near the bottom. 

 (To be continued.) 



Practical Scheme. — Through the kindness of Mr. J. T. 

 Neeve, of 4, Sydenham Road, Deal, I am able to offer for dis- 

 tribution four named varieties of Marine Algae, mounted on 

 paper, which can be kept either as herbarium specimens, or can be 

 mounted as microscopic objects, for which latter they should be 

 soaked in soft or rain water for twenty-four hours, which will 

 cause the specimens to assume their natural state. Then mount 

 in Dean's medium or glycerine jelly. If mounted in balsam in 

 the dried state the cells are distorted and shortened. The 

 instructions given for the mounting of Fungi, a few weeks ago, 

 are also recommended by Mr. Neeve. 



Applicants for these Marine Algaj are requested to enclose 

 with the Coupon appearing in the advertisement ])ages of this' 

 number, a stamped, directed, square envelope, about 'i in. by 4 in. 

 Particular attention is drawn to this ])oint as it considerably 

 reduces the amount of labour involved in this distribution. 



Should any readers of this journal wish for further specimens, 

 I should recommend them to apply direct to Mr. Xeeve, at the 

 address given above, who is both an authority and an enthusiast in 

 this particular work. ►», 



NOTES AND QUERIES. 



Lt. Diimant. — -The following would be the best manner for 

 cutting sections of Marine Worms, to show the arrangement of 

 parts: — ^Pin the worm, slightly on the stretch, on a strip of 

 wood and harden in methylated spirit for ten days, changing 

 the spirit every day for the first three days. Then cut the 

 specimen up into pieces about \ in. long, place these in absolute 

 alcohol and transfer to equal parts of absolute alcohol and ether 

 and soak for about twelve hours. Place in a thin solution of 

 celloidin for about twelve hours, transfer to a thicker solution 

 of celloidin for twelve hours. Remove from celloidin on the 

 point of a needle and expose to the action of the air until the 

 celloidin drys, then jjush off with a needle into methylated 

 spirit and soak for twelve hours to complete hardening of the 

 celloidin. Place the infiltrated portion of worm between two 

 pieces of carrot, fit it to the embedding arrangement of the 

 Cathcart Microtome and make the sections. Stain in Grenacher's 

 carmine, wash out excess of stain in methylated spirit acidulated 

 with hydrochloric acid, one part acid and .mx of spirit. Then 

 wash well in methylated spirit and place in absolute alcohol for 

 two or three minutes, no lon','er, clear in oil of origanum and 

 mount in Canada balsam. If jireferable, the pieces of worm 

 may be stained in bulk in carmine before they are infiltrated 

 with celloidin. Permanganate of potash is used for de- 

 colourising sections when ovetstained with carmine, but the 

 acidulateil spirit answers quite as well and gives less trouble. 



W. S. Rollers. — The most likely way to remove the siliceous 

 matter is to boil the material in a weak solution of bi-c.;irbonate 

 of soda. If this is not succes-ful the only alternative is to 

 select the specimens from the ili-hr/.i by hand. 



Pinacoid. — The only two makers of binocular dissecting 

 stands of such low power as you require are Zeiss and Leitz. 

 but it seems doubtful to me if either of them will exactly meet 

 your conditions as to portability. The majority of such 

 instruments are fitted with jirisms at t'le eyepiece end, and 

 have two tubes which are inclined at an angle one to the other, 

 and neces-sitate the use of two objectives. Leitz's binocular 

 preparation microscope, consisting of two Briicke lenses niacrni- 

 fying four diameters, only costing C:!, can bj taken to pieces for 

 packing, and is of consiiler ible value for preparation purposes. 

 I think j'ou would be bettor suited with an ordinary singlo lens 

 dissecting microscope. Any London hcuse would send you 

 lists or particulars of Leitz or Z-^iss microscopes. 



ir. S. liii.rler.—l am sorry it is impossible to accede to your 

 request ; there are many simple explaoations of Numerical 

 Aperture given in various works on the mioroscopj, the perusal 

 of which will give von the lUsii-, d iMf.imi itimi. 



