The presence, however, of apparatus or observers upsets the conditions, while above uneven ground or near a tree or a building the equipotential surfaces cease to be horizontal.
Cells treated by reagents, has been interpreted by many observers as a network of threads embedded in a homogeneous ground-substance.
In Spirogyra the pyrenoids are distinctly connected by cytoplasmic strands to the central mass of cytoplasm, which surrounds the nucleus, and according to some observers, they increase exclusively by division, followed by a splitting of the cytoplasmic strands.
Many observers hold the view that the chromosomes are pulled apart by the contraction of the fibres to which they are attached.
Some observers consider that it represents a longitudinal half of the original segment of the spireme, others that it is a half of the segment produced by transverse division by means of which a true qualitative separation of the chromatin is brought about.
It has since been shown by other observers that this double fertilization Occurs in many other Angiosperms, both Dicotyledons and Monocotyledons, so that it is probably of general occurrence throughout the group (see ANGIOSPERMS).
Rosenberg (1909) adduces evidence fox the existence of chromosomes or prochromosomes in resting nuclei in a large number of plants, but most observers consider that the chromosomes during the resting stage become completely resolved into a nuclear network in which no trace of the original chromosomes can be seen.
The central body probably plays the part of a nucleus and some observers consider that it has the characters of a typical nucleus with mitotic division.
Some observers consider that the yeast nucleus possesses a typical nuclear structure, and exhibits division by mitosis, but the evidence for this is not very satisfactory.
Rend., 1888, 106, p. 1357.) The gas may be liquefied by a pressure of about 17 atmospheres, the liquid so obtained boiling at - 61.8° C.; and by further cooling it yields a solid, the melting point of which is given by various observers as - 82° to - 86° C. (see Ladenburg, Ber., 1900, 33, p. 6 37).
From time to time there have been observers who have maintained a belief in the opposite theory, to which the name heterogenesis has been given.
To the first belong what may be called the physical phenomena (q.v.) of spiritualism - those, namely, which, if correctly observed and due neither to conscious or unconscious trickery nor to hallucination or illusion on the part of the observers, exhibit a force acting in the physical world hitherto unknown to science.
Probably most persons who have studied the subject would now be inclined to go this length; and there is some evidence, notably in connexion with the trances of an American medium, Mrs Piper,' which has convinced some good observers that the hypothesis of occasional communication from deceased persons must be seriously entertained.
The strange contrast between the succession of dynasties and kings cut off by assassination in the northern kingdom, ending in the tragic overthrow of 721 B.C., and the persistent succession through three centuries of the seed of David on the throne of Jerusalem, as well as the marvellous escape of Jerusalem in 701 B.C. from the fate of Samaria, must have invested the seed of David in the eyes of all thoughtful observers with a mysterious and divine significance.
From the time of Hippocrates onwards the malarial or periodical fevers have engaged the attention of innumerable observers, who have suggested various theories of causation, and have sometimes anticipated - vaguely, indeed, but with surprising accuracy - the results of modern research; but the true nature of the disease remained in doubt until the closing years of the 19th century.
Quartan and malignant types of fever, have been described by Italian observers, and the classification is generally accepted;.
The first was that people who got it and survived never got it again; that had been noted centuries before by the Persian physician and by numerous observers since.
With a little more deliberation in the choice of their pursuits, all men would perhaps become essentially students and observers, for certainly their nature and destiny are interesting to all alike.