May, 1902.] 



KN OWLEDGE 



117 



them, would have absolutely no chaiic<' of life. It is sufj- 

 gested by Dr. S'ansfield that ajio-spory may be an atavie 

 trait — "a character that may have been general or even 

 universal iu the infancy of the race. This idea is borne 

 out to some extent by the fact that apospory is favoured 

 by a uniformly humid atmosphere, a condition which 

 probably prevailed in early geologic (say Silurian and 

 Devonian) times."* A still more remarkable" short cut " 

 has been detected recently by Mr. W. H. Lang, when 

 experimenting with apogamous ferns. Iu a Carnarvon- 

 shire variety of the Broad Buckler Fern, Laxlrea dilalata, 

 var. cristahi (jracilh, and a inuch-branched variety of the 

 Hart's-tongue, Si-nlo/iendriiiDi (•«/;/« rd, var. raiiiulosi.inlminii, 

 that observer discovered that sporangia were borne ou the 

 prothallia, thus cutting out the whole asexual or fern- 

 plant generation. t 



So, as Mr. Druery remarks in a recent* summing-up of 

 the question, " it has been now demonstrated that in the 

 sequence of spore, prothallus, antheridia, archegouia, 

 fertilized seed and spore-bearer, every one of the steps, 

 without exception, can be eliminated altogether ; thus 

 apospory cuts out the spore and even the sjioix'-hcap ; 

 bulbils on the fronds or elsewhen'. cut out the prothallus ; 

 ajiogamy cuts out the antheridia, antherozoids, archegouia, 

 and fertilized seed ; and the spore-bearing prothallus cuts 

 out the sporojihore proper." 



XoTE. — Till- Writer's bot thanks are duo to his IVieiid, Mr. C. T. 

 Druery, til Dr. F. W. Stansfield, ami to tlie Cotiiu'il of llie liinueun 

 t'oeielj', for peruiission to reproduce or adapt Vigs. -1 to 8, from the 

 Society's Journal. 



Af 



Conducted by M. I.Cros,s». 



PoNM Cni.i.E( TiNc; IN M.iY. — All the various pond organisms 

 that die down in winter and in various ways produce protected 

 germs to tide over this, for them, unsuitable season, will now have 

 come to life again and begin to multiply at an increasing rate. 

 Many kinds of Desmids should be found in shallow, mossy pools, 

 or along the edge of rivulets. Among Protophyta and Protozoa 

 the green spheres of ]'olvo.r (ihilnitur will be found in many 

 localities more or less abundantly, and the various kinds of 

 Acineta should be looked for in quiet, undisturbed waters, 

 where many kinds of free-swimming Infusoria will also be 

 found. 



Of Rot if era there aro few species which may not be found 

 in May. At one excursion of the Quekett Club to Totteridge 

 in. the middle of May forty different species were obtained. 

 To mention only a few : Nolups brdchioniw, one of the most 

 attractive Rotifers, will have made its appearance, then various 

 kinds of .Inififn, A'<jilinirlui<i, Hniehinnus, Coelopus, Ciilhi/jjini, 

 DiiiMhi'd, I'licliltini.i, Furcularia, Manlif/ncerca, Mefupiiiid, 

 Pterodhiti, Siiiicliwfii,Stejtliininji>i, Scaridiiiiii : also filc/ilidiioi-i'roit 

 eirhhoniii, I'lo/^iiilex, .^telhrrta, and Limniax in abundance. 



On rootlets of trees growing near the edge of ponds and lakes 

 will i)robabIy be found various kinds of Polyzoa : FredericeUu 

 SiiUiiiiii, I'ahiilircllii and I'luuiatilla repen.i. 



Attach.mii.k :^[I:( hankai. STAr.r.s. — Many workers com- 

 mence with a microscope of plain construction, and as the scope 

 of their work increases tind a mechanical stage a real necessity : 

 especially is this the case with students. For ordinary biological 

 and histological purposes a i)lain stage is not only sufficient but 

 frequently found to be the most suitable, for with constant 



* Loccit. t ^roc. Roy. Soc, LX., p. 250,1896. Phil. Tram., 



CXC, B.,p. 1»7, 1898. I Gardeners' CAroniWe, March 30, 1901. 



]>ractice the fingers become educated to moving the object with 

 accuracy and with a rapidity which could not well be attained 

 with a mechanical stage. But when a ,'. in. oil immersion is added 

 and systematic examination of a specimen over its entire surface 

 is necessary, and not merely a general observation of its 

 characteristics, the fingers fail to do what is needed. To meet 

 such cases the attachable mechanical stage was devised, and 

 judging by the many patterns that are offered, no small amount 

 of ingenuity has been put into their construction. They 

 un(|uestionably su])p!y a need, but it cannot be too strongly 

 emiihasised bow far inferior they are to a good mechanical stage 

 built as a part of the microscope. The fewer detachable parts 

 there are in the instrument the greater is the possibility of 

 afEording that rigidity which is such a prime necessity. Take 

 any of the attachable mechanical stages, and none of them are 

 really free from some defect ; they have to be self-contained, 

 and as the space in which they work is of necessity constricted, 

 the bearings and fittings have to be of the lightest description, 

 with the result that they rarely work truly, and if they receive 

 a fall or knock are almost irremediably damaged. For any rack 

 and pinion to engage and work responsively and without back- 

 lash the rack must be firmly bedded, and this cannot be 

 accomplished so well in any other form as the fixed stage ; no 

 rack with its teeth set on end will ever be nearly so satisfactory. 

 Further, in the attachable stage, when power is put into the 

 millcd-head, there is a tendency to shake or lift the attachment; 

 this is an impossibility with the fixed stage. 



In view of these facts it is worthy of consideration whether 

 an attachable mechanical stage can be really accepted as a 

 desirable addition to a microscope. The Continental makers, 

 with the exception of Zeiss and Reichert, in their largest 

 photographic stands provide the attachable patterns only, and 

 where necessity has demanded the addition of a mechanical 

 object carrier to a plain stage instrument, its u.se can be readily- 

 understood, but the price charged for them is so high that in 

 nearly all English-made microscopes it is possible to exchange 

 the plain stage for a good fixed mechanical jiattern at the same 

 or even less cost, and seeing that the modern fixed mechanical 

 stages are made with a large plain surface ou which the 

 specimen can be manipulated with the fingers when low powers 

 are employed, it is to be recommended that a fixed mechanical 

 stage should at all times be obtained where possible, and the 

 attachable form in cases of unavoidable necessity only. 



Two-speed Fjjje Ao.rusTMENT. — I called attention in the 

 February number to a new two-speed fine adjustment which 

 had been introduced by Messrs. R. & J. Beck, and another 

 interesting device to secure the same result, but by other means, 

 has been devised by ilessrs. Watson i**: Sons. In this case, a 

 single screw only is used, the differences of speed being obtained 

 by two milled heads of diilerent diameters, one being attached 

 to the other. It is an old idea which has been used in micro- 

 meter gauges and spectroscopes and is here applied to the 

 microscope. 



If a large milled head be turned by the thumb 

 and first finger, it wiO be found that the rotation 

 is eft'ected very slowly, but if that milled head 

 were one-sixth of the size, it could be turned 

 with six times the rapidity, and herein is the 

 very simple explanation of the little application 

 to Watson's fine adjustment. 



The disadvantage of this arrangement is that 

 work will be done by the fine adjustment which 

 should more properly fall to the rackwork coar.se 

 adjustment, consequently, in course of time the 

 single fine screw will be likely to show more signs of wear than 

 the coarse screw used Vjy Messrs. Beck for their slower speed, 

 but in any case the action is so simple and effective that there is 

 no reason why every microscope should not be provided with it. 



Preparing Mycetozoa. — Mr. M. J. Cole gives the following 

 instructions for mounting these specimens : — Most of these 

 fungi can be mounted dry in glycerine jelly after soaking in 

 equal parts of rectified spirit and glycerine to remove the air, 

 but in those forms which possess lime granules in the capil- 

 litium — a character of importance in classification — the cal- 

 careous matter disappears when in glycerine in any form Where 

 this is the case, place the specimens in absolute alcohol until all 

 air is removed, then transfer to clove oil, and when clear, mount 

 in Canada balsam. 



