Imatges de pàgina
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and burrow into the substance of the plant attacked. But more commonly, the contents of the spore divide into six or eight separate portions. The coat of the spore gives way, and each portion then emerges as an independent organism, which has the shape of a bean, rather narrower at one end than the other, convex on one side, and depressed or concave on the opposite. From the depression, two long and delicate cilia proceed, one shorter than the other, and directed forwards. Close to the origin of those cilia, in the substance of the body, is a regularly pulsating contractile vacuole. The shorter cilium vibrates actively, and effects the locomotion of the organism, while the other trails behind; the whole body rolling on its axis with its pointed end forwards.

The eminent botanist, De Bary, who was not thinking of our problem, tells us, in describing the movements of these "Zoospores," that, as they swim about, "foreign bodies are carefully avoided, and the whole movement has a deceptive likeness to the voluntary changes of place which are observed in microscopic ani

mals."

After swarming about in this way in the moisture on the surface of a leaf or stem (which, film though it may be, is an ocean to such a fish) for half an hour, more or less, the movement of the zoospore becomes slower, and is limited to a slow turning upon its axis, without change of place. It then becomes quite quiet, the cilia disappear, it assumes a spherical form, and surrounds itself with a distinct, though delicate, membranous coat. A protuberance then grows out from one side of the sphere, and, rapidly increasing in length, assumes the character of a hypha. The latter penetrates into the substance of the potato-plant, either by entering a stomate or by boring through the wall of an epidermic cell, and ramifies, as a mycelium, in the substance of the plant, destroying the tissues with which it comes in contact. As these processes of multiplication take place very rapidly, millions of spores are soon set free from a single infested plant; and from their minuteness they are readily transported by the gentlest breeze. Since again, the zoospores set free from each spore, in virtue of their powers of locomotion, swiftly disperse themselves over the surface, it is no wonder that the infection, once started, soon spreads from field to field, and extends its ravages over a whole country.

However, it does not enter into my

present plan to treat of the potato-disease, instructively as its history bears upon that of other epidemics; and I have selected the case of the Peronospora simply because it affords an example of an organism, which, in one stage of its existence, is truly a "monad," indistinguishable by any important character from our Heteromita, and extraordinarily like it in some respects. And yet this monad can be traced, step by step, through the series of metamorphoses which I have described, until it assumes the features of an organism, which is as much a plant as an oak or an elm is.

Moreover it would be possible to pursue the analogy further. Under certain circumstances, a process of conjugation takes place in the Peronospora. Two separate portions of its protoplasm become fused together, surround themselves with a thick coat, and give rise to a sort of vegetable egg called an oospore. After a period of rest, the contents of the oospore break up into a number of zoospores like those already described, each of which, after a period of activity, germinates in the ordinary way. This process obviously corresponds with the conjugation and subsequent setting free of germs in the Heteromita.

But it may be said that the Peronospora is, after all, a questionable sort of plant; that it seems to be wanting in the manufacturing power, selected as the main distinctive character of vegetable life; or at any rate, that there is no proof that it does not get its protein-matter ready made from the potato-plant.

Let us, therefore, take a case which is not open to these objections.

There are some small plants known to botanists as members of the genus Coleochate, which, without being truly parasitic, grow upon certain water-weeds, as lichens grow upon trees. The little plant has the form of an elegant green star, the branching arms of which are divided into cells. Its greenness is due to its chlorophyll, and it undoubtedly has the manufacturing power in full degree, decomposing carbonic acid and setting free oxygen under the influence of sunlight.

But the protoplasmic contents of some of the cells of which the plant is made up occasionally divide, by a method similar to that which effects the division of the contents of the Poronospora spore; and the severed portions are then set free as active monad-like zoospores. Each is oval and is provided at one extremity with two long active cilia. Propelled by these,

it swims about for a longer or shorter time, but at length comes to a state of rest and gradually grows into a Coleo

chate.

Moreover, as in the Peronospora, conjugation may take place and result in an oospore; the contents of which divide and are set free as monadiform germs.

If the whole history of the zoospores of Peronospora and Coleochate were unknown, they would undoubtedly be classed among "monads " with the same right as Heteromita; why then may not Heteromita be a plant, even though the cycle of forms through which it passes shows no terms quite so complex as those which occur in Peronospora and Coleochate? And, in fact, there are some green organisms, in every respect characteristically plants, such as Chlamydomonas, and the common Volvox, or so-called "globe animalcule," which run through a cycle of forms of just the same simple character as those of Heteromita.

The name of Chlamydomonas is applied to certain microscopic green bodies, each of which consists of a protoplasmic central substance invested by a structureless sac. The latter contains cellulose, as in ordinary plants; and the chlorophyll which gives the green colour enables the Chlamydomonas to decompose carbonic acid and fix carbon, as they do. Two long cilia protrude through the cell-wall, and effect the rapid locomotion of this "monad," which, in all respects except its mobility, is characteristically a plant.

domonads; and which progresses with a rotating motion effected by the paddling of the multitudinous pairs of cilia which project from its surface. Each Volvoxmonad has a contractile vacuole like that of Heteromita lens, and moreover possesses a red pigment spot like the simplest form of eye known among animals.

The methods of fissive multiplication and of conjugation observed in the monads of this locomotive globe are essentially similar to those observed in Chlamydomonas; and though a hard battle has been fought over it, Volvox is now finally surrendered to the botanists.

Thus there is really no reason why Heteromita may not be a plant; and this conclusion would be very satisfactory, if it were not equally easy to show that there is really no reason why it should not be an animal.

For there are numerous organisms presenting the closest resemblance to Heteromita, and, like it, grouped under the general name of "monads," which, nevertheless, can be observed to take in solid nutriment, and which therefore have a virtual, if not an actual, mouth and digestive cavity, and thus come under Cuvier's definition of an animal. Numerous forms of such animals have been described by Ehrenberg, Dujardin, H. James Clark and other writers on the infusoria.

Indeed, in another infusion of hay in which my Heteromita lens occurred, there were innumerable infusorial animalcules belonging to the well-known species Col poda cucullus.*

Under ordinary circumstances the Chlamydomonas multiplies by simple fis- Full-sized specimens of this animalcule sion, each splitting into two or into four attain a length of between one threeparts, which separate and become inde- hundredth or .0025 of an inch, so that pendent organisms. Sometimes, how-it may have ten times the length and ever, the Chlamydomonas divides into a thousand times the mass of a Heteeight parts, each of which is provided romita. In shape it is not altogether unwith four, instead of two cilia. These zoospores conjugate in pairs, and give rise to quiescent bodies, which multiply by division, and eventually pass into the active state.

like Heteromita. The small end, however, is not produced into one long cilium, but the general surface of the body is covered with small actively vibrating ciliary organs, which are only longest at the small end. At the point which answers to that from which the two cilia arise in Heteromita, there is a conical depression, the mouth; and in young specimens a tapering filament, which reminds one of the posterior cilium of Heteromita, projects from this region.

Thus, so far as outward form and the general character of the cycle of modifications through which the organism passes in the course of its life are concerned, the resemblance between Chlamydomonas and Heteromita is of the closest description. And on the face of the matter there is no ground for refusing to admit that The body consists of a soft granular Heteromita may be related to Chlamy-protoplasmic substance, the middle of domonas, as the colourless fungus is to which is occupied by a large oval mass the green alga. Volvox may be compared to a hollow sphere, the wall of

Excellently described by Stein, almost all of whose

which is made up of coherent chlamy-statements I have verified.

called the "nucleus; " while, at its hinder | progress - here the line between the aniend, is a "contractile vacuole," conspicu- mal and the plant must be drawn. ous by its regular rhythmic appearances and disappearances. Obviously, although the Colpoda is not a monad, it differs from one only in subordinate details. Moreover, under certain conditions, it becomes quiescent, incloses itself in a delicate case or cyst, and then divides into two, four, or more portions, which are eventually set free and swim about as act-modern investigation is in favour of the ive Colpola.

But this creature is an unmistakable animal, and full-sized Colpode may be fed as easily as one feeds chickens. It is only needful to diffuse very finely ground carmine through the water in which they live, and, in a very short time, the bodies of the Colpode are stuffed with the deeply coloured granules of the pigment.

There is reason to think that certain organisms which pass through a monad stage of existence, such as the Myxomycetes, are, at one time of their lives, dependent upon external sources for their protein-matter, or are animals; and at another period manufacture it, or are plants. And seeing that the whole progress of doctrine of continuity, it is a fair and probable speculation-though only a speculation that, as there are some plants which can manufacture protein out of such apparently intractable mineral matters as carbonic acid, water, nitrate of ammonia, and metallic salts; while others need to be supplied with their carbon and nitrogen in the somewhat less raw form of tartrate And if this were not sufficient evidence of ammonia and allied compounds; so of the animality of Colpoda, there comes there may be yet others, as is possibly the the fact that it is even more similar to an- case with the true parasitic plants, which other well-known animalcule, Parama- can only manage to put together materials cium, than it is to a monad. But Para- still better prepared still more nearly mæcium is so huge a creature compared approximated to protein until we arrive with those hitherto discussed it reaches at such organisms as the Psorospermia one one-hundred-and-twentieth of an inch and the Panhistophyton, which are as or more in length-that there is no diffi- much animal as vegetable in structure, but culty in making out its organization in de-are animal in their dependence on other tail; and in proving that it is not only an organisms for their food. animal, but that it is an animal which possesses a somewhat complicated organization. For example, the surface layer of its body is different in structure from the deeper parts. There are two contractile vacuoles, from each of which radiates a system of vessel-like canals; and not only is there a conical depression continuous with a tube, which serve as mouth and gullet, but the food ingested takes a definite course and refuse is rejected from a definite region. Nothing is easier than to feed these animals and to watch the particles of indigo or carmine accumulate at the lower end of the gullet. From this they gradually project, surrounded by a ball of water, which at length passes with a jerk, oddly simulating a gulp, into the pulpy central substance of the body, there to circulate up one side and down the other, until its contents are digested and assimilated. Nevertheless, this complex animal multiplies by division, as the monad does, and, like the monad, undergoes conjugation. It stands in the same relation to Heteromita on the animal side, as Coleochate does on the plant side. Start from either, and such an insensible series of gradations leads to the monad that it is impossible to say at any stage of the

The singular circumstance observed by Meyer, that the Torula of yeast, though an indubitable plant, still flourishes most vigorously when supplied with the complex nitrogenous substance, pepsin; the probability that the Peronospora is nourished directly by the protoplasm of the potato-plant; and the wonderful facts which have recently been brought to light respecting insectivorous plants, all favour this view; and tend to the conclusion that the difference between animal and plant is one of degree rather than of kind; and that the problem whether, in a given case, an organism is an animal or a plant, may be essentially insoluble.

From Temple Bar. HER DEAREST FOE.

CHAPTER XXXIX.

WELCOME as he ever was, Tom Reed was perhaps never so anxiously looked for as on the present occasion. Kate felt that he could disentangle the ravelled skein of her affairs; that he only could deal with Trapes; and his tact so manipulate the difficulties with which her relations

to Galbraith bristled, as to effect a fair | a hearty hug, a long, loving kiss, put every. division of the property she hoped to thing and every one save the donor out of prove her own, without letting Galbraith Fanny's head. "It seems a hundred know her identity until it was accom- years since I saw you, my darling," cried plished. Tom, who, though looking a little thin and worn, was in high spirits and full of animation. "You little, ungrateful, saucy coquette! you are as blooming and bright as if I had been at your elbow all the time! Where is the pale cheek and teardimmed eyes that ought to show the sincerity with which you mourned my absence, and the severe mental arithmetic you exercised counting the days till I came?"

Kate enjoyed the rare advantage of being in sympathy with her adviser. Generally an adviser is an enemy, whose opinions, ranged under a different banner from one's own, are to be in some way circumvented or twisted into accord with the advised: or, possessing sufficient weight to impose them upon the bearer, they are so often acted upon in an unwilling spirit as to neutralize their possible good effect.

But there was a real accord between Tom Reed and the young widow; even when they differed, each knew that he or she was thoroughly understood by the other.

Fanny was of course in a state of unconcealable joy. She had stolen half an hour in the afternoon to compound a lobster currie for the late dinner or early supper at which Tom was expected. A low and mundane method of preparing for a lover's reception perhaps, in the reader's opinion, but ask the lover's-!

--

The trains between Stoneborough and Pierstoffe were by no means patterns of punctuality, and the friends agreed not to expect Tom till quite half an hour after he was due. That half an hour was nearly exhausted, when their attention was diverted by the entrance of Mills with a note, an untidy note without an envelope, and fastened by a wafer. It was directed to T. Reed, Esq., in a very intoxicatedlooking hand.

"This has just been brought by a boy from the Shakespeare Inn, ma'am, and he wants to know if Mr. Tom is come."

"Say he has not, but we expect him every moment," replied Mrs. Temple, scanning the note critically. "This is from Trapes, no doubt."

"Don't you think we might open it?" insinuated Fanny, laying a couple of covetous little fingers on it. "It is all about yourself, of course. I really think you might read it, Kate."

"Ah, Tom, I should have had a dash of uncertainty to reduce me to the proper condition of paleness and dimness. But I know you, and I am at rest," a small responsive hug, and some half-uttered ejaculations interrupted, as may be imagined.

"I see I do not go the right way to work to show what a valuable article I am!" cried Tom.

"If you worried, or gave me any trouble, should not care a straw about you," said Fanny, with a pretty moan.

I

"Now let me call Kate, she is dying to see you."

"I think she might give us a few minutes more law."

"Oh, here, Tom, is a note for you!" cried Fanny, darting to the mantelpiece and taking it down. "I believe it is from that strange man, Mr. Trapes."

"Trapes!" echoed Tom, in much surprise. "How does he know that I am here?"

"Oh, because-but I will leave Kate to tell everything. Just do look at the note!"

"There! you may discount your rights, if you choose," said Tom, laughing, and handing the scrawled morsel of paper to her.

"What a hand! What is that word?" "Seriously.""

"Read it to me, dear Tom."

"My dear Reed, I am seriously ill, and cannot go to see you as I promised Mrs. T. I feel as if I was near the You impatient puss! I think we might end of the race, and nowhere! Look in wait for Tom to read his own correspond-on me, like a brick, to-morrow. ence. He will be here in a quarter of an hour if he comes at all."

"Ah, Kate, that is a cruel 'if'!" "Never fear, Fan- there, there is some conveyance stopping at the door. Here he is, and I shall run away!"

"Indeed, Kate, indeed you need not!" But Kate was gone. The next moment

"Yours,

G. TRAPES.' "If Trapes knocks up, he will not last long," said Tom, gravely; "but call Mrs. Travers. I long to hear all about everything!"

"Now tell me how you unearthed Trapes?" asked Tom.

They were sitting round the fire after dinner, Mrs. Temple having insisted on his refreshing himself before going into any discussion of business.

"He came to the surface of his own accord," she replied, and proceeded to describe her encounter with him clearly and shortly, till she came to the part performed by Galbraith, where she broke down for an instant, paused, collected herself, and continued her narrative by a decided abridgment. "When I was sufficiently recovered to walk home, Sir Hugh Galbraith was good enough to come part of the way, and I have not seen him since." She then passed rapidly on to Trapes's evening visit, and his remarkable boast: "I can produce the man who drew out the will, two or three months after Mr. Travers's death; and I can produce the man that employed him to do it!"

"This is very extraordinary," said Tom, when Kate ceased speaking. "If Trapes can make good his promise, of course your success is an accomplished fact. But I must warn you that my former acquaintance is given to the wildest romancing at times. Still, I believe he does know something of importance. One point, however, I must press upon you, Mrs. Temple do not see this scamp any more - leave him to me." "Most willingly and Tom." "Very well. Now, do you think he recognized Galbraith?"

thankfully, dear

"No; I do not think he did." "Mind," continued Tom, "I don't think it matters a straw whether he tells his tale to Galbraith or to you, if he can support it; for of course, a man of Galbraith's position and character would not for a moment hesitate about restoring your rights. All I want to make sure of before we stir in the matter is, to be prepared with irresistible proof. As things are at present, we should only be knocking our heads against the stone wall of a long lawsuit were you to move. However, you must leave Trapes to me." There was a pause, during which Tom appeared lost in thought a condition which Kate and Fanny respected too much to disturb. At last he roused himself, and assumed the attitude peculiar to Britons when about to dictate or domineer - that is, he placed himself on the hearth-rug, with his back to the fire. "It was a remarkable, though fortunate accident that Sir Hugh Galbraith came to your assistance. Is it permitted to ask what brought him to Pierstoffe just in the nick of time?" And

Tom, with an air of comical solemnity, paused for a reply.

Kate crimsoned even over her little ears, but answered steadily, though in a low voice, "No, Tom, you must not ask. I cannot tell you any fibs, so I would rather say nothing."

"Ahem!-and in spite of this gallant rescue and unexpected appearance - I presume it was unexpected?"

"Most unexpected!" she returned. "You are determined to carry the war into the enemy's country?"

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Quite determined!" said Kate rising and coming to the fire, where she leaned against the chimney-piece, " if I can bring an overwhelming force to bear upon his position."

"Do you mean to say," exclaimed Tom, quickly, darting one of his keenest glances at the fair, downcast face before him, "that you have any fresh cause for vengeance?"

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"For vengeance? oh, no!" she returned, looking frankly into his eyes. My opinion of Sir Hugh is changed for the better. It is for his sake as well as my own that I wish matters hurried on."

"You are incomprehensible!" he returned, less amiably than usual.

"Then do not try to comprehend me," she said, gently laying her hand on his arm, "but act as if the chapter of accidents had never brought Hugh Galbraith to lodge under my roof-continue to be my best friend as you have been."

"You generally make slaves of your friends," replied Tom, resignedly. "However, I have not opened my budget yet. I saw Wall this morning. He had just had S―'s opinion, and showed it to me. He considers that there are grounds for taking criminal proceedings against Poole."

"And will Mr. Wall arrest him, then?" asked Kate, anxiously.

"No. He would in the first instance summon Poole to answer the charge of having wilfully perjured himself by swearing that he was present when Mr. Travers executed the second will. But, as nothing could be done till Monday, I advised his waiting my return before he took any step, thinking there might be something in your idea that Trapes could give us information that would implicate Ford."

"And he can, depend upon it, Tom!" said Kate, thoughtfully. "I dropped a hint that perhaps his information might be more valuable to Mr. Ford than to me, and I saw his countenance change unmistakably."

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