Sphere

(sfer). I. A ball or globe. 2. A space. S. of Attraction, a clear spot in the cell-plasma, outside of and close to the nucleus of an ovum undergoing mitosis. It contains the centrosoma of Boveri, and is the center of the formation of the amphiasters in karyokinesis, q. v. S. -crystal. Same as Sphceraphide. S., Embryonic. See S., Segmentation-. S.-Granule, a large granular corpuscle found in serous exudations. S., Hearing, the area in the brain which is supposed to be the seat of hearing. It is in the temporal lobe. S., Motor, a region in the central nervous system which, when stimulated, gives rise to motion. S., Protoplasmic Primordial. See S., Segmentation-. S., Segmentation-, a nucleated cell derived from division of the vitellus in the proce of segmentation. S., Sensory, a sensory area of the central nervous system. S., Vitelline, S., Yolk-, the mulberry-like ma of cells that results from the fi ion of the substance of the ovum after fertilization. S., Yeast-, in biology, an aggregation of certain sprouting forms of the genus Mucor.