Talk:Book - Embryology of the Pig 2
Gametes from Parent Generation
Fertilized Ovum
Somatic Cells
cells which continue to proliferate and by countless cell divisions and by divergent specialization give rise to the body. Vlth death of individual these cells cease to exist.'
gives rise to new individual*
Cleavage Divisions and indefinite number
of succeeding cell divisions during early growth of embryo
Certain cells become recognizable as
the Primordial Sex Cells
and become established in the gonads of the embryo.
Give rise to other units in the gonad similar to those indicated below.
Female Embryos become sexually differentiated
Male
In the growing ovary of embryo ovigerous cords and egg nests ~ arc formed
0og(
lonia
During youth odgonia remain quiescent.
In some cases oogonia 1 may be augmented in numbers during sexual maturity
Very slowly and only a few at a time oogonia grow
In the growing testes of the embryo seminiferous tubules are organized.
Spermatogonia
During youth spermatogonia remain relatively inactive.
y/V During sexual activity y-v spermatogonia augment their numbers by active division.
fVlmary Oocyte
Secondary Obeytes
/Body
rarely divides
Ootids Polar
In each maturation division Body all the stored food goes to one cell which is destined to be the ovum. The small cells receiving no yolk are called
S olar bodies, Thby never toone functional.
c/bmocx)Jb
Following the growth period of either spermatogonium or oSgonium. two maturation divisions rapidly succeed each other. In one of these divisions the species number of ohromosomes is reduced a half.
Mature
Ovum
Any spermatogonium may at any time cease dividing temporarily and grow into a
Primary Spermatocyte
which by first maturation division forms
Two Spermatocytes
second maturation division
Four Spermatids .
Without further divisions the spermatids beoome differentiated into
Spermla
Fertilisation of ovum by spermlum inltiatee development of new individual of filial generation*
(Speoios tniaiber of ohromosomee restored,)
Fig. 4. Chart outlining, for one generation, the history of the gametes and the germ plasm from which they are derived.