446 The Botanical Gazette. [November, 
definite spheres each with a dense center, which he consid- 
ered as permanent cell organs in connection with the nucleus. 
In the following year Boveri(1) observed the sphere and its 
center. He called the dense central body the centrosome, 
and regarded it as a contribution from the spermatozoon to 
the attraction-sphere of the ovum. 
Distribution.—Investigations were made on various kinds 
of sexual cells until the year 1891, when Flemming (5) first 
found the attraction-spheres and centrosomes in the resting 
stages of leucocytes and in the epithelial cells of the lungs of 
the salamander. In the same year Guignard (10) demon- 
strated the existence of these bodies in reproductive vegetable 
cells, both in the resting stage and during karyokinesis. Since 
that time they have been found in the cells of many kinds of 
tissues, and especially in the ova of various animals. 
Heidenhain (14) found them in the leucocytes of the sala- 
mander, in the medullary cells of the bones of young rabbits, 
and in the alveolar epithelium and leucocytes of the lung of a 
pneumonic patient; Biirger(3), in the proboscis-sheath of 
nemerteans, in resting cells; van der Stricht, (29) in the blas- 
tomeres of Triton and in the cartilaginous cells of several 
amphibia; E. de Wildeman(32), in Spirogyra and in the spore- 
mother-cells of Equisetum; Biitschli(4), in Surirella; and 
Schottlinder (25), in the antheridia of Gymnogramme and in 
the spermatozoids and the ova of Chara. Heidenhain (153) 
in a recent investigation has made a special study of centro- 
somes in the lymph cells (lymphocytes) and giant cells (me- 
gacaryocytes) from the bone marrow of the rabbit. He foun 
them also in the spleen of the rabbit, and in the lymphatic 
gland and the wall of the intestine of the dog. Thus the 
bodies have been demonstrated in reproductive cells of both 
plants and animals, and also in non-reproductive animal cells. 
General description.—The general appearance of a centro- 
some and its surrounding attraction-sphere is described by 
van Beneden (28) as a dense ‘‘cytocenter” around which may 
be distinguished a medullary and a cortical zone concentric to 
the central corpuscle. Heidenhain (15) also lays emphasis 
on the fact that the attraction-sphere is sharply limited from 
the surrounding protoplasm, and in many cases shows @ 1% 
tinct radiate ‘structure. Guignard (10) says, in regard to te 
bodies seen by him in plant cells, that the attraction-spheres 
were composed of transparent granular areas in which 
a ee, 
