July 13, 1883.] 



- KNOWLEDGE ♦ 



17 



AN ILOLSTRATED 



MAGMNEof^IENCE 



PUmrripRDED -£XACTl|DESCRIBED 



LONDON: FRIDAY, JULY 13, 1883. 



Contents op No. 89. 



PAOB. 



Pleasant Hours with the Micro- 

 scope. By H. J. Slack, F.G.S., 

 F.R.M.S. iniu8.) 17 



Chemistry of the Cereals. — I. By 

 W. Jago, F.C.S IS 



Geology and Agriculture. — II. By 

 J. V. Elsden.F.C.S., &c 19 



Australian Ants {co»t.) 21 



Sea Anemones at the Fisheries 



Exhibition, {Illus.) By Thonias 

 Kimber, M.A., Lond 23 



Mr. Stephen Leslie on the Influ- 

 ence of Science 



The Brush Dynamo-Electric Ma- 

 chine. (Iltits.) 



Fiffure Conjuring. ByR. A. Proctor 



Editorial Gossip 



The Divided Skirt 



Something about the Beet 



Correspondence 



Our Mathematical Column 



Our Chess Column 



PLEASANT HOURS WITH THE 

 MICROSCOPE. 



By Henry J. Slack, RG.S., F.RM.S. 



THE figures now given illustrate the descriptions in 

 the last paper, and show some of the principal 

 varieties of infusoria. They will also enable some in- 

 teresting questions concerning their movements to be con- 

 sidered. Motion that looks more or less like voluntary is 

 by no means confined to the animal world. Motile spores 

 of algif, for example, are very common, and there are few 

 objects more fascinating than the exquisite emerald-spangled 

 globes of volvox swimming with the aid of numerous cilia. 

 There are no sharp boundaries between the animal and 

 vegetable worlds, but as advances from the lowest forms 

 are examined, a positive preponderance of character is dis- 

 covered. Speaking generally, the respiration of plants is 

 like that of animals. They absorb oxygen and evolve 

 carbonic acid ; but they can also digest that acid, and 

 use its carbon to build up their structures, which 

 thorough animals cannot do. The chlorophyl of 

 plants is the agent for effecting this process, and a 

 few animals which possess it — Euglenre', for example — 

 may have a similar power. In proportion as organisms 

 exhibit decidedly animal characteristics, we might expect 

 their movements to appear more likt; the ir ill-directed 

 actions of the higher orders, and this is generally true. 

 When moving objects jostle together, go to the edge of a 

 containing cell and stick there, or in any other way appear 

 blundering, they probably belong to the vegetaV)le world. 

 Mr. Saville Kent, whose opinion is entitled to great weight, 

 finds that as a rule the animal types " make tentative, well- 

 controlled progress in various directions, and intelligent 

 deviations." Let us investigate this. Fig. 1 shows a 

 minute creature {Ikleromtla lens) with a small whip ; the 

 little group of dots are its spores. The magnification is 

 800 linear. Many much smaller objects swim skilfully by 

 means of similar whips. In this group and in many others, 

 Mr. Kent observes that the movements seem to be intelli- 

 gently guided. It is impossible without intolerable circum- 

 locution to speak of these things with accurate precision. 



In using such a word as intelligence, it does not mean the 

 same as if it were applied to a human being, but something 

 on a lower platform, in some respects resembling it. Fig. 2, 

 a and A, are EiKjknoi (F. viridis). They were formerly 

 placed by most authors amongst the plants, but Mr. Kent 

 confirms the observations which assign to them a small 

 mouth, and he succeeded in inducing them to swallow 

 minute particles of carmine. On this, and on other 

 accounts, he claims them as animals. 



On a sunny day, go to a quiet pond that is covered, or 

 streaked, with a thin scum, like green-pea soup. Skim a 

 little into a bottle, and the capture most likely consists of 

 myriads of beautiful little fish-like things of emerald 

 lustre, with a so called ruby eye-speck. These are 

 Uugleua:. There are several species ; the commonest 

 — the one figured — varies from 1-1150" to 1-240" in 

 length. The bottle containing them should be kept in 

 the light, to promote their development. In the dark they 

 sink to the bottom ; the light brings them to the surface. 

 They are furnished with a remarkably elastic integument, 

 and can assume all sorts of odd shapes, or a globular one. 

 Our object now is to watch their swimming. A drop of 

 the water containing them is placed in a little glass cell, 

 100th of an inch deep. This gives them plenty of room 

 for moving at different depths. A half-inch objective, 

 with A or B eye-piece and dark-ground illumination, 

 shows them off well. Continual watching rarely detects a 

 collision. For hours together they swim backwards and 

 forwards, this way and that, often with sudden changes of 

 direction as sharp as those of a swallow or bat. If one is 

 comparatively quiet, a little ripple amongst floating par- 

 ticles proclaims the motion of the long, whip-like swimming 

 organ, but the lash itself is invisilile, or very troublesome 

 to see with any power while the creature is active ; and 

 when it rounds itself, and lies still, it is not displayed. 

 To see it, put a droplet of tincture of iodine, as big as a 

 pin's head, on a glass slide ; then add a rather larger 

 droplet of water containing the creatures ; put gently over 

 them a thin covering glass. They all die ofl'-hand, and the 

 whips are then so plain that we wonder they were not seen 

 before. They are rather longer than the animal, and their 

 arrested motion leaves them in wavy or twisted patterns. 

 The swimming is sometimes assisted — perhaps entirely 

 caused — by contractions and expansions of the integument ; 

 but often the queer changes of shape must make it more 

 dilEcuIt for the whip to move the creature, as it does, in a 

 definite way. Fig. .5 is a Paramecium, with plentiful rows 

 of cilia, but its motions are not so wonderful as those 

 effected by the whip of the Euglemt. Where a cilium is 

 highly magnified, and its motion becomes slow as the water 

 dries up, it is seen to be much like what can be 

 done with a long flexible cane, held in the hand, and 

 worked by sharp turns of th(^ wrist A wave motion runs 

 from the base to the tip. When an animalcule uses a 

 quantity of these organs, rhythmical agreement is the chief 

 thing necessary; but how to row a canoe with a whip-lash 

 is quite another matter. Whips and cilia are commonly 

 described as the same things, only difiering in stiffness. 

 Watching the work of the whips leads tlie present writer 

 to regard them as very diflerent things. The Etirjlnm has 

 its whip at the mouth (red speck end), and it pulls itself 

 forwards through the water, with rapid changes of direc- 

 tion. It is impossible to conceive this could be done by 

 moving the whip by an impulse from its base only, as is the 

 case with cilia. Tlu' whole length of the whip appears 

 highly vitalised, whil(> the cilium is only an elastic bristle 

 of a delicate description. A curve at any part must 

 modify the direction of the currents produced by its lash- 

 ing, and as the motions always look skilful and purposeful, 



