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has recently received important extensions through the noteworthy experiments of Nussbaum1 and of Gruber, who have demonstrated independently the possibility of dividing unicellular animals so that each piece will regenerate the missing parts. In this manner the number of individuals can be artificially multiplied. For example: Nussbaum divided a well-isolated Oxytricha into two equal parts, either transversely or longitudinally, and found that the edges of the cut became soon surrounded with new cilia. Although some of the substance of the body, or even a nucleus, was lost through the operation, yet, by the following day, the two parts converted themselves into complete animals with four nuclei and nucleoli (nebenkerne) and the characteristic ciliary apparatus. The head-piece has formed a new hind end; the right half, a new left half." The new-formed duplicate Infusoria multiplied subsequently by spontaneous division. From one Oxytricha cut in two, Nussbaum succeeded in raising ten normal animalcules, which subsequently all encysted. After an unequal division, the parts are both still capable of regeneration, but parts without a nucleus did not survive; which suggests that the formative energy is in some way bound up with the nucleus. But nucleate pieces may break down. Thus all attempts at artificial multiplication of the multinucleate Opalina failed, although the division of Actinosphaerium had been successfully made by Eichhorn as long ago as in the last century. Pelomyxa palustris has been successfully divided by Greef, and Myxastrum radians by Haeckel.
Gruber (1. c., p. 718) describes his experiments with Stentor: "If one divides a Stentor transversely through the middle, and isolates the two parts, one finds on the cut surface of the hind part, after about twelve hours, a complete peristomial field with the large cilia and buccal spiral newly formed. On the other hand, the piece on which the old mouth is situated has elongated itself backwards, and attached itself in the manner peculiar to these Infusoria. If one has made a longitudinal section, so that the peristom is cut in two, then the peristoms both complete themselves, and the lateral wounds heal over. I have repeatedly separated by trans-section pieces considerably less than half of the original Stentor, and these have also regenerated themselves to complete animals." Gruber, too, observed that
1 M. NUSSBAUM. Veber spontane und künstliche zelltheilung. Sitzungsb. Niederrhein. ges. nat. u. heilkunde. Bonn, Dec. 15, 1884. [I regret very much that I know this paper only by Gruber's abstract.]
2 A. GRUBER. Veber künstliche teilung bei Infusorien. Biolog. centralbl., iv. (No. 23) 717-722.
artificially divided Infusoria were capable of subsequent spontaneous multiplication. If the section is not very deep, there may arise double monsters; but here, just as in spontaneous divisions, as long as there remains an organic connecting-band, the two parts act as one individual, showing that the nervous actions are not restricted to determined paths. Gruber also adds, that two divided pieces may be reunited, if they are brought together again quickly enough. The observation thus briefly announced is of such extreme interest and importance, that the publication of the full details of the experiment will be eagerly awaited. Gruber adds, that at present we cannot go much beyond the proof of the existence, to a high degree, of the regenerative capacity in unicellular organisms. He also makes the significant observation, that, in the Protozoa, we have to do foremost with changes of function; in the Metazoa, with growth also.
2. Duplication of parts. In these anomalies we find an organ which, although an extra member, yet still conforms to the type of the species. For example: a frog is found with three posterior limbs; dissection proves the third leg to agree anatomically with the typical organization of the frog's hind leg. In determining the importance to be attributed to this evidence, it should be remembered, on the one hand, that these instances are by no means unusual; on the other, that the agreement with the normal structure is not uniform. 3. Asexual reproduction. When a species multiplies by fission of any kind, we must assume that each part, after division, possesses the formative tendency, since we see it build up what is necessary to complete the typical organization of the individual. Again: a bud of a hydroid or polyzoon, although comprising only a small part of the body, is equally endowed with this uncomprehended faculty. In pseudova we reach the extreme limit: in Aphis, for example, the parent gives off a single cell, the capacity of which to produce a perfect and complicated individual, fully equals the like capacity of a hydroid bud or of half a worm.
The evidence forces us to the conclusion that the formative force or cause is not merely the original disposition of the forces and substances of the ovum, but that to each portion of the organism is given, 1. The pattern of the whole organism; 2. The partial or complete power to reproduce the pattern. italicised formula is, of course, a very crude scientific statement, but it is the best which has occurred to me.
The formative force, then, is a diffused tendency. The very vagueness of the expression serves to emphasize our ignorance concerning the real nature of the force. In this connection, I venture to insist upon the fact that we know little or nothing concerning any of the fundamental properties of life, because I think the lesson of our ignorance has not been learned by biologists. We encounter not infrequently the assertion that life is nothing but a series of physical phenomena; or, on the other hand, what is less fashionable science just now, that life is due to a special vital force. Such assertions are thoroughly unscientific; most of them are entirely, the remainder nearly worthless. Of what seem to me the prerequisites to be fulfilled before a general theory of life is advanced, I have written elsewhere.1 CHARLES S. MINOT.
DURING the last few years the number of electric wires in all of our large cities has rapidly increased, especially since the introduction of the telephone and the electric light; and the probability is that the next few years will show a further large increase. If these wires run on poles, they not only disfigure the streets, but seriously interfere with the operations of firemen, as we have repeatedly seen during the last few years. A cobweb of wires supported on housetops requires the line-men to continually tramp through the houses and over the roofs, causing annoyance to the tenants, and damage to the buildings. Moreover, wires fixed to housetops are subject to removal at the whim of the owner, and they have to be continually removed from building to building as the good will of each owner is exhausted. Again: overhead wires, whether placed on poles or housetops, are continually coming in contact with each other, causing annoyance and danger; and an extra heavy rain or sleet storm so entangles and breaks them as to entirely interrupt communication. The annual cost of repairs of overhead wires in cities is not less than thirty per cent of the first cost of construction.
In almost all of the large cities the question is being asked, Why cannot these wires be gathered into cables and buried, along with the gas and water pipes, under the streets? In answer, it is proposed to review briefly the technical difficulties that arise, and to show how they may be and are overcome.
1 C. S. MINOT. On the conditions to be filled by a theory of life. Proc. Amer. assoc. adv. sc., xxviii. 411.
proposed, further, to compare the cost of construction and maintenance of overhead wires with the cost of construction and maintenance of underground cables, and thus to see which is desirable from economical considerations.
There are two reasons, apart from the difficulty of securing good insulation, why underground lines are comparatively inefficient:
1. If an electric conductor be brought near to a large mass of conducting-matter, as is a wire when it is taken down from a pole and buried in the earth, there appears in the current the phenomenon of retardation, by which each signal, instead of being sharp and distinct, is partly kept back, so that it overlaps and mingles with the next. The result is to limit the speed of working of the apparatus, or, if, like the telephone, it be an apparatus in which the currents are necessarily extremely frequent, to confuse and destroy the signals altogether.
2. The second difficulty is called induction, and is noticed when two or more wires are run side by side and near together, as they necessarily are in an underground cable. If the signals on one wire of such a cable be sharp and quick, they cause facsimile signals on all of the neighboring wires; and this, too, though the insulation may be absolutely perfect. The result of this phenomenon is, that messages sent over one wire are liable to be received on all of the other wires; and in telephony each person can easily overhear all that the others are saying.
Fortunately, however, both of these difficulties vary with the electrical qualities of the cable; and while I have seen cables of a thousand feet, over which it was difficult to talk, and in which the cross-talk was nearly as loud as the direct conversation, on the other hand, I have conversed easily over an underground cable extending from Paris to Orleans, eightyfive miles; and this, too, while other parties similarly separated were talking over other conductors of the same cable. There was absolute secrecy.
Last summer I visited France and Germany, and made, together with Mr. Berthon (chief engineer of the French telephone company), Mr. Cäel (chief engineer of the French government telegraph), and Herr Guillaume (constructor of the underground lines of the German empire), a series of telephone experiments on underground lines, varying from 5 to 100 miles in length, from 2.87 to 48 ohms resistance, and from 0.06 to 0.35 microfarads capacity per mile.
These experiments furnish us with ample
2. High insulation; for without this the current leaks from one conductor to the others, giving rise to cross-talk; and it is possible to talk by direct leakage between two conductors whose insulation is several million ohms.
3. Low specific inductive capacity; for, the greater the capacity, the greater the retardation, and the greater also the cross-talk due to induction.
Below is a table showing the specific inductive capacity and insulation of various insulators. The measurements were all made on a wire 0.05 of an inch in diameter, coated with insulation to a thickness of 0.10 of an inch.
Let us take a special case, and compare a gutta-percha cable having a specific inductive capacity of 4.2 with a Faraday cable of 1.6. The table predicts that we can talk three times as far with the latter as with the former, and experiment shows that we can. Again: the cross-talk on the gutta-percha cables ought to greatly exceed that on a Faraday cable; and experiment has shown, that, while conversation over a two-mile gutta-percha cable was continually disturbed by existing cross-talk, conversation was carried on over a similarly constructed Faraday cable five miles in length without the cross-talk being appreciable.
By proper attention to the electrical qualities, then, we may talk underground a much greater distance than we shall ever have reason to in any city system, and this without crosstalk from the neighboring circuits.
We have seen that telegraph and electriclighting currents are not subject to the technical difficulties we have been discussing, and that, provided good conductivity and good insulation are assured, it is with them purely a question of expense. Let us, then, determine the relative expense of overhead and underground wires. Suppose we have a large city with a telegraphoffice near the centre, and that it is desired to
carry a hundred wires to the city limits, say, three miles distant. Let us suppose that the wires for the first mile rest on housetops, and for the remainder of the distance on poles. The cost will be:
That is, the relative first cost of an overhead and an underground line, to do the same work, would be, say, $14,000 and $24,000.
The same conclusion will hold true for telephone-wires, provided we confine ourselves to the problem of running out from the central office, by fifty or a hundred conductor cables, to a large number of distributing-points so situated about the city that any subscriber would be easy of access, by a short overhead line, to one or another of them; and this is the problem that really occurs. So much for construction.
The yearly cost of repairing an overhead system, including roof-rentals, is not less than thirty per cent of the cost of construction; and the line would have to be renewed once in twelve years. The cost of repairing an underground system is practically nil. The Paris telephone company, with wires extending to three thousand subscribers, does not keep any repair-men. The durability of an underground system, provided lead-covered cables are used, and there is no internal cause of deterioration, is at least thirty years. Last summer we examined some lead-incased gutta-percha cables that had been in use by the French government for that length of time, and found them in perfectly good condition. The same is true of India-rubber cables incased in lead.
Herr Guillaume says of a cable in use by the German government, similar to the Faraday cable, "We are using it altogether in our new construction. I do not see how it can ever decay. We tried cotton-covered wires soaked in paraffine and drawn into lead pipes; and, though they worked well at first, after a few years they failed."
W. W. JACQUES, PH.D., Electrician of the American Bell telephone co.
REDUCED FACSIMILE OF DRAWINGS SHOWING SOME EVIDENCE OF SO-CALLED THOUGHT-TRANSFERENCE.
issued a circular during the winter, describing some simple experiments in guessing digits or
persons making the trials according to the directions of the circular, and the results will
be published in the first number of the proceedings of the society, which will appear during the summer. Besides these set experiments, Mr. W. H. Pickering of Boston met with some success in the experiments which have attracted so much attention from the English society, experiments in which a drawing thought of by one person, is reproduced by another, who has no visible means of obtaining information as to what the drawing may be. In the accompanying illustration we have reproduced all the figures as they were drawn, numbering them from 1 to 52. The upper line in each case contains the originals, and the lower the reproductions. The originals were made either by Mr. Pickering or by one of his friends, and the reproductions were most of them made by a young lady, who, on one or two evenings when the experiments were tried, met with some success. It may be well to state, that with figs. 6, 7, 8, and 20, certain extraneous causes acted which interfered with the results. The first forty figures were all made in one day; figs. 41 to 47 inclusive were made by another person; the remaining figures were made by the sensitive, so called, on a day when apparently there was no thought-transference.
MIMICRY AMONG MARINE MOLLUSCA.
It is a curious fact, that, while among the terrestrial animals the number of known cases of protective mimicry is very large, among aquatic animals it is very small. I have no doubt that the comparative poverty of our knowledge of the habits and situation of aquatic animals in part accounts for this, but I believe also that there is really vastly less mimicking. I do not know of any marine species, that, harmless in themselves, mimic formidable species for protection; but there are instances in which forms are modified in color or shape so as to resemble the surroundings in which they live, and thus escape the observation of their enemies. In the summer of 1879, Dr. E. B. Wilson, while studying in Brooks's laboratory at Beaufort, N.C., found abundant specimens of Ovulum uniplicatum, -a mollusk living upon the stems of Leptogorgia virgulata (a sea-fan abundant there in shallow sounds). The stem of the sea-fan is of an orange-yellow color, and, further, is often marked with yellow swellings where the coral has spread itself over the shell of an attached barnacle. The Ovulum has a yellow shell; and the skin folds up over the shell, and is also of an orange-yellow color, -precisely the same color as that of the pen
natulid, so that the snail escapes notice very readily indeed. It is abundantly found upon the Leptogorgia, and never met with except associated with it. Last summer at Beaufort, in trawling in ten fathoms of water, a few miles off Cape Lookout, we took a Leptogorgia whose general habit was the same as that of L. virgulata, but which was very different from it in color. In this one the color is deep rose, almost purple, and mottled with white at the openings, where the polyps are fixed. Now, the question was, Is there an Ovulum for this Leptogorgia? and on examination, sure enough, there was found a large number of the Ovulums, in this case again imitating the colors of the host. This Ovulum is undoubtedly of the same species as the yellow one, for it presents no difference except in color. The shell is redbrown; and the folds of skin that surround it in the expanded snail are deep-rose color, and mottled with white spots. Here, then, is another very good illustration of the familiar principle that forms will vary in adaptation to their surroundings, and of the part that mimicry may play in natural selection. Confined
in aquaria, the snails sought their own corals to creep over them; and, if the red snail and yellow coral only were put into the same aquarium, the snail showed not the least desire to creep over the coral, but remained creeping about the walls of the aquarium.
I observed another snail last summer that I feel sure must owe its shape and color, at least in part, to mimicry, though here there were not so good grounds for the conviction as in the case just mentioned. I found on the beach at Fort Macon, one day after a strong southerly gale, a single specimen of an undetermined species of Scyllaea, a nudibranch characterized by a pair of tentacle shields, and two pairs of elongate narrow processes of the skin upon the back, on the inner side of which white delicate gills are placed. This creature, when placed upon the Sargassum, or gulf-weed, shows the closest resemblance to it. The color is almost identical with that of the alga, a light brown. The body is elongate and much compressed, and the foot-sole an elongate, narrow groove, perfectly adapted for adhering to the alga stem. The tentacle sheaths and the skin processes upon the back are thin, and at the edges are wavy, and present the most perfect resemblance to the leaves (?) of the alga. The compressed body is further terminated posteriorly by a thin vertical portion like a fin,
1 Dr. W. Breitenbach, in Popular science monthly, January, 1885, p. 365, mentions vaguely some nudibranch that imitates the sea anemones upon the stems of Sargassum.