In Hydra viridis the polyp is of a green colour and produces a spherical egg with a smooth shell which is dropped into the mud.

The practical difficulty of constructing Gregorian telescopes of good defining quality is very considerable, because if spherical mirrors are employed their aberrations tend to increase each other, and it is extremely difficult to give a true elliptic figure to the necessarily deep concavity of the small speculum.

Ptolemy Euergetes (247-222 B.C.) rendered the greatest service to geography by the protection and encouragement of Eratosthenes, whose labours gave the first ap proximate knowledge of the true size of the spherical The .

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The chloroplast consists of two parts, a colorless ground substance, and a green coloring matter, which is contained either in the form of fibrils, or in more or less regular spherical masses, in the colorless ground-mass.

The motion of the bob of a spherical pendulum, i e.

The spherical aberrations, however, can be overcome, or at least so diminished that they are quite harmless, by forming appropriate combinations of lenses.

The female flowers (cones) vary considerably in size; the largest are the more or less spherical cones of Araucaria - a single cone of A.

Smith) bears very definite terminal, or intercalary, spherical vesicles, which may probably be regarded as reproductive organs - either oiigonia or sporangia.

For the subjects of this heading see the articles DIFFERENTIAL EQUATIONS; FOURIER'S SERIES; CONTINUED FRACTIONS; FUNCTION; FUNCTION OF REAL VARIABLES; FUNCTION COMPLEX; GROUPS, THEORY OF; INFINITESIMAL CALCULUS; MAXIMA AND MINIMA; SERIES; SPHERICAL HARMONICS; TRIGONOMETRY; VARIATIONS, CALCULUS OF.

The Structure of the Nucleus.In the living condition the resting nucleus appears to consist of a homogeneous ground substance containing a large number of small chromatin granules and one or more large spherical granulesnucleolithe whole being surrounded by a limiting membrane which separates it from the cytoplasm.