. Outlines of zoology. Zoology. 666 MAMMALIA. is formed containing fluid, and into this cavity the follicle cells immediately surrounding the ovum project, forming what is called the discusproligerus. (See Fig. 198, p. 467.) When mature, the ovum protrudes on the surface of the ovary, and is liberated by the bursting of the Graafian fol- licle. Some blood, which fills up the empty follicle, degener- ates into what is called the corpus luteum. The spermatozoa are formed from germinal epithelium in the testes. The primitive male cells or spermatogonia give rise by division to daughter cells or s
. Outlines of zoology. Zoology. 666 MAMMALIA. is formed containing fluid, and into this cavity the follicle cells immediately surrounding the ovum project, forming what is called the discusproligerus. (See Fig. 198, p. 467.) When mature, the ovum protrudes on the surface of the ovary, and is liberated by the bursting of the Graafian fol- licle. Some blood, which fills up the empty follicle, degener- ates into what is called the corpus luteum. The spermatozoa are formed from germinal epithelium in the testes. The primitive male cells or spermatogonia give rise by division to daughter cells or spermatocytes, which, with or without further division, form spermatozoa. The homologue of the ovum is the spermatogonium or mother - sperm - cell, but the physiological equivalent of the ovum is the spermatozoon. No one has succeeded in satisfactorily observing an ex- trusion of polar bodies in the maturation of the mammalian ovum, but analogous processes occur at an early stage. The ovum, having burst from the ovary, is immediately caught by the fimbriated mouth of the Fallopian tube, and begins to pass down the ovi- duct. There it is met by ascending spermatozoa, re- ceived by the female as the result of sexual union, and is fertilised. One of the spermatozoa enters the ovum, and sperm nucleus unites with ovum nucleus in an intimate and orderly Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Thomson, J. Arthur (John Arthur), 1861-1933. Edinburgh, Glasgow and London, H. Frowde and Hodder & Stoughton
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Keywords: ., bookauthorth, bookcentury1800, bookdecade1890, booksubjectzoology
