Polar Bodies, the minute cells which are separated from the egg in its maturation divisions.
Primate (L. primus, first), the highest order of animals, including monkeys, apes and man.
Pronucleus, the nucleus of the mature ovum or sperm-cell.
Protoplasm (Gr. protos, first; plasma, form), the essential living substance.
Protozoa (Gr. protos, first; zoon, animal), single-celled animals or animals composed of cells not separable into different tissues.
Psychical (Gr. psyche, the soul), pertaining to the mind.
Recessive Character (L. recessus, a going back), a character from one parent which remains undeveloped in offspring when associated with the corresponding dominant character from the other parent.
Reduction Division, a division of the maturing germ-cells in which the dual or somatic (diploid) number of chromosomes is reduced to the single (haploid) number.
Reflex Action (L. re, back; flectere, bend), an automatic response of the nervous and motor mechanism of the body.