yal or noble house.

COHEN (Hebrew for "priest"), a Jewish family name, implying descent from
the ancient Hebrew priests. Many families claiming such descent are,
however, not named Cohen. Other forms of the name are Cohn, Cowen, Kahn.

See J. Jacobs, _Jewish Encyclopedia_, iv. 144.

COHN, FERDINAND JULIUS (1828-1898), German botanist, was born on the
24th of January 1828 at Breslau. He was educated at Breslau and Berlin,
and in 1859 became extraordinary, and in 1871 ordinary, professor of
botany at Breslau University. He had a remarkable career, owing to his
Jewish origin. He was contemporary with N. Pringsheim, and worked with
H. R. Goeppert, C. G. Nees von Esenbeck, C. G. Ehrenberg and Johannes
Muller. At an early date he exhibited astonishing ability with the
microscope, which he did much to improve, and his researches on
cell-walls and the growth and contents of plant-cells soon attracted
attention, especially as he made remarkable advances in the
establishment of an improved cell-theory, discovered the cilia in, and
analysed the movements of, zoospores, and pointed out that the
protoplasm of the plant-cell and the sarcode of the zoologists were one
and the same physical vehicle of life. Although these early researches
were especially on the Algae, in which group he instituted marked
reforms of the rigid system due to F. T. Kutzing, Cohn had already
displayed that activity in various departments which made him so famous
as an all-round naturalist, his attention at various times being turned
to such varied subjects as _Aldorovanda_, torsion in trees, the nature
of waterspouts, the effects of lightning, physiology of seeds, the
proteid crystals in the potato, which he discovered, the formation of
travertin, the rotatoria, luminous worms, &c.

It is, however, in the introduction of the strict biological and
philosophical analysis of the life-histories of the lower and most
minute forms of life that Cohn's greatest achievements consist, for he
applied to these organisms the principle that we can only know the
phases of growth of microscopic plants by watching every stage of
development under the microscope, just as we learn how different are the
youthful and adult appearances of an oak or a fern by direct
observation. The success with which he attempted and carried out the
application of cultural and developmental methods on the Algae, Fungi
and Bacteria can only be fully appreciated by those familiar