Oct. 30, 1884] 



NA TURE 



647 



seconds there is no disconnected sarcode visible, and in five to 

 seven minutes the organism is a union of two of the organisms, 

 the swimming being again resumed, the flagella acting in appa- 

 rent concert. This may continue for a short time, when move- 

 ment begins to flag and then ceases. Meanwhile, the bodies 

 close together, and the eyenots or vacuoles melt together, the 

 two nuclei become one and disappear, and in eighteen hours 

 the entire body of "either has melted into other," and a 

 motionless, and for a time irregular, sac is left. This now 

 becomes smooth, spherical, and tight, being fixed and motion- 

 less. This is a typical process ; but the mingled weariness and 

 pleasure realised in following such a form without a break 

 through all the varied changes into this condition is not easily 

 expressed. 



But now the utmost power of lenses, the most delicate 

 adjustment of light, and the keenest powers of eyesight and 

 attention must do the rest. Before the end of six hours the 

 delicate glossy sac opens gently at one place, then there streams 

 out a glairy fluid densely packed with semi-opaque granules, 

 just fairly visible when their area was increased six millions 

 of times, and this continued until the whole sac was empty 

 and its entire contents diffused. To follow with our utmost 

 powers these exquisite specks was an unspeakable pleasure, a 

 group seen to roll from the sac, when nearly empty, were 

 fixed and never left. They soon palpably changed by appa- 

 rent swelling or growth, but were perfectly inactive ; but at 

 the end of three hours a beaked appearance was presented. Rapid 

 growth set in, and at the end of another hour, how has entirely 

 baffled us, they acquired flagella and swam freely ; in thirty-five 

 minutes more they possessed a nucleus and rapidly developed, 

 until at the end of nine hours after emission a sporule was followed 

 to the parent condition and left in the act of fission. In this way, 

 with what difficulties I need not weary you, a complete life-cycle 

 was made out. 



And now I will invite your attention to the developmental 

 history of the most minute of the six forms we studied. In form 

 it is a long oval, it is without visible structure or differentiation 

 within, and is possessed of only a single flagellum. Its 

 utmost length is the 5000th of an inch. Its motion is con- 

 tinuous in a straight line, and not intensely rapid, nor greatly 

 varied, being wholly wanting in curves and dartings. The 

 copiousness of its increase was, even to our accustomed eyes, 

 remarkable in the extreme, but the reason was discovered with 

 comparative ease. Its fission was not a division into two but 

 into many. The first indication of its approach in following 

 this delicate form was the assumption rapidly of a rounder 

 shape. Then followed an amoeboid and uncertain form, 

 with an increased intensity of action which lasted a few mo- 

 ments when lassitude supervened, then perfect stillness of the 

 body, which is now globular in form, while the flagellum feebly 

 lashed, and then fell upon and fused with the substance of the 

 sarcode. And the result is a solid, flattened, homogeneous ball 

 of living jelly. 



To properly study this in its further changes, a power of from 

 three to four thousand diameters must be used, and with this I 

 know of feu things in the whole range of minute beauty more 

 beautiful than the effect of what is seen. In the perfectly 

 motionless flattened sphere, without the shiuimer of premonition 

 and with inconceivable suddenness, a white cross smites itself, 

 as it were, through the sarcode. Then another with equal 

 suddenness at right angles, and while with admiration and 

 amazement one for the first time is realising the shining 

 radii, an invisible energy seizes the tiny speck, and fixing 

 its centre, twists its entire circumference, and endows it 

 with a turbined aspect. From that moment intense interior 

 activity became manifest. Now the sarcode was, as it were, 

 kneading its own substance, and again an inner whirling motion 

 was v i le, reminding one of the rush of water round the interior 

 of a hollow sphere on its way to a jet or fountain. Deep fissures 

 or indentions showed themselves all over the sphere ; and then 

 at the end of ten or more minutes all interior action ceased, and 

 the sphere had segmented into a coiled mass. There was 

 no trace of an investing membrane ; the constituent parts were 

 related to each other simply as the two separating parts of an 

 ordinary fission ; and they now commenced a quick, writhing 

 motion like a knot of eels, and then, in the course of from seven 

 to thirty minutes separated, and fully endowed with flagella 

 swam freely away, minute but perfect forms, which by the rapid 

 absorption of pabulum attained speedily to the parent size. 



It is characteristic of this group of organic forms that multi- 



plication by self-division is the common and continuous method 

 of increase. The other and essential method was comparatively 

 rare and always obscure. In this instance, on the first occasion 

 the continuous observation of the same "field " for five days failed 

 to disclose to u< any other method of increase but this multiple- 

 fission, and it was only the intense suggestiveness of past 

 experience that kept us still alert and prevented us from in- 

 ferring that it was the only meth id. But eventually we perceived 

 that while this was the prevailing phenomenon, there were 

 scattered amongst the others forms of the same m jnad larger 

 than the rest, and with a singular granular aspect towards the 

 flagellate end. It may be easily contrasted with the normal or 

 ordinary fo> m. Now by doggedly following one of these through 

 all its wanderings a wholly new phase in the morphology of the 

 creature was revealed. This roughened or granular form seized 

 upon and fastened itself to a form in the ordinary condition. The 

 two swam freely together, both flagella being in action, but it 

 was shortly palpable that the larger one was absorbing the lesser. 

 The flagellum of the smaller one at length moved slower, then 

 sluggishly, then fell upon the sarcode, which rapidly diminished, 

 while the bigger form expanded and became vividly active until 

 the two bodies had actually fused into one. After this its activity 

 diminished, in a few minutes the body became quite still, leaving 

 only a feeble motion in the flagellum, which soon fell upon the 

 body-substance and was lost. All that was left now was a still 

 spheroidal glossy speck, tinted with a brownish yellow. A pecu- 

 liarity of this monad is the extreme uncertainty of the length of 

 time which may elapse before even the most delicate change in this 

 sac is visible. Its absolute stillness may continue for ten or more 

 hours. During this time it is absolutely inert ; but at last the sac 

 — for such it is — opens gently, and there is poured out a brownish 

 glairy fluid. At first the stream is small, but at length its flow 

 enlarges the rift in the cyst, and the cloudy volume of its contents 

 rolls out, and the hyaline film that inclosed it is all that is left. 



The nature of the outflow was like that produced by the 

 pouring of strong spirit into water. But no power that we could 

 employ was capable of detecting a granule in it. To our most 

 delicate manipulation of light, our finest optical appliances, and 

 our most riveted attention, it was a homogeneous fluid and 

 nothing more. This for a while baffled and disturbed us. It 

 lured us off the scent. We inferred that it might possibly be a 

 fertilising fluid, and that we must look in other directions for the 

 issue. But this was fruitless, and we were driven again to the 

 old point, and having once more obtained the emitted fluid, de- 

 termined to fix a lens magnifying 5000 diameters upon a clear 

 space over which the fluid had rolled, and near to the exhausted 

 sac, and ply our old trade of watcking-xmbrdken observation. 



The result was a reward indeed. At first the space was clear 

 and white, but in the course of a hundred minutes there came 

 suddenly into view the minutest conceivable specks. I can only 

 compare the coming of these to the growth of the stars in a 

 starless space upon the eye of an intense watcher in a summer 

 twilight. You knew but a few minutes since a star was not 

 visible there, and now there is no mistaking its pale beauty. It 

 was so with these inexpressibly minute sporules ; they were not 

 there a short time since, but they grew large enough for our 

 optical aids to reveal them and there they were. Such a field 

 after one hour's watching I present to you. And here I would 

 remark that these delicate specks were unlike any which we saw 

 emerge directly from the sac as granules. In that condition they 

 were always semi-opaque, but here they were transparent, and 

 a brown yellow, the condition always sequent upon a certain 

 measure of growth. 



To follow these without the loss of an instant's vision was 

 pleasure of the highest kind. In an hour and ten minutes from 

 their first discovery they had grown to oval points. In one hour 

 more the specks had become beaked and long. And this pointed 

 end was universally the end from which the flagellum emerged. 

 With the flagellum comes motion, and with that abundant pabu- 

 lum, and therefore rapid growth. But when motion is attained 

 we are compelled to abandon the mass and follow one in all its 

 impetuous travels in its little world ; and by doing so we are 

 enabled to follow the developed speck into the parent condition 

 and size, and not to leave it until it had, like its predecessors, 

 entered on and completed its wonderful self-division by fission. 



It becomes then clearly manifest that these organisms, lowly 

 and little as they are, arise in fertilised parental products. There 

 is no more caprice in their mode of origin, than in that of a 

 crustacean or a bird. Their minuteness, enormous abundance, 

 and universal distribution, is the explanation of their rapid and 



