Picture - Cosmic Polymath

384 DESIGN IN NATURE
PLATE LXXXVII
PLATE LXXXVII (continued)
(R, S, T.) Stages o£ metakiiiesis according to Rabl.
R. The split chromosomes beginning to separate.
S. The separation further advanced.
T. The separated chromosomes passing along the fibres of the achromatic spindle.
U. Gland-cell from a larva of nemocera. a, Cell membrane ; h, protoplasm ; c, nucleus with convoluted filament.
V. Part of the nuclear filament seen at U greatly magnified (Carnoy).
PLATE LXXXVIII
Plate Ixxxviii. illustrates the formation and conjugation of the pronuclei in Ascaris megalocephala according to
E. V. Beneden.
A. a, Female pronucleus ; h, male pronucleus, each containing two chromatin particles, the male (h) exhibiting skein formation ;
c, one of the polar globules ; the second polar globule has been extruded.
B. The chromatin in the female (a) and male (J) pronuclei forming skeins ; r , polar globule.
C. The skein formation of the female (a) and male (h) pronucleus more pronounced ; remains of spermatozoon adhering to b.
Two attraction-spheres (d) with central particles united by spindle of achromatic fibres now appear ; c, polar globule.
D. The female (a) and male (h) pronuclei enlarged and skein formation completed ; c, polar globule.
E. a, Female pronucleus with skein contracted and thickened ; d, attraction-spheres on one side of ovum connected with
periphery by cone of fibres forming polar circle (e, e') ; f, equatorial circle.
F. Female (a) and male (ft) pronuclei now in contact ; spindle system arranged across their axes. The attraction-spheres {d, d),
placed between pronuclei. At G, H, I, and J, these spheres are omitted.
G. Construction of skein and v-shaped formation of chromatin filaments in female (n) and male (b) pronuclei, which now indent
each other ; c, polar globule.
H. V-shaped chromatin filaments more pronounced, and union of female (a) and male (5) pronuclei more intimate ; c, polar
globule.
I. V-shaped chromatin filaments dividing by longitudinal cleavage a and h, male and female pronuclei ; r, polar globule.
J. Highly magnified
c, polar globule.
to show structure of v-shaped chromatin filaments {a, b) ; consist of fine granules of chromatin ;
K. a, b, Four chromatin loops in middle of elongated ovum about to divide into two cells ; the loops forming a spindle-shaped
system of granule with fibrils radiating in the direction of the attraction-spheres (d, d'), which in turn radiate into the protoplasm
of the ovum ; c, polar globule.
L. Shows chromatin filaments (a, b) of conjugated nuclei separating; also system of radiating fibres from attraction-spheres
{d, d') ; c, c polar circle ,
; d, d', central circle ; e, equatorial circle (semi-diagrammatic).