1887] The Significance of Sex. 143 
Fic. 120. Cell from testis of Chelonia caja—Carnoy, p. 250.—The nuclear spindle 
is nearly constricted off in the equator; the ‘hpi: is partly so, and shows its 
T as ri dis goo arranged as those of the spind] 
1. Dividing sperm-cells from Aat—Weidersperg, A. m. A., xxv.—The two 
sat i are at a distance from each other, but still the Abie fibres unite the two 
daughter-nuclei. 
PLATE VIII. 
Fic. 122, a-¢, From pollen mother-cells of Fritillaria persica—Strasburger, A. 
m. A., xxiii.—a-g is the SA pet -m the anaphase, m-r a succeeditig prophase, 
and r-¢ the next anaphase he filament is at first much finer pap more intricately 
woven than represented in the een three diagrams. In ġ we see a nucleolus at one 
ih in connection with which the loops of the skein are put; ¢ is a polar view of the 
d the filament has shortened more and passed out of its relation with the 
te sadist which is now breaking down. Next, in ¢, the segmentation is com- 
pleted, and the limbs of the U-shaped segments are closely applied to each other; 
then, in 7, these stumpy “loops” get crowded into the centre, and the spindle is 
formed (g). Then splitting ensues and metakinesis (4). In the daughter-nuclei the 
loops come to lie so as to make the poles of the nucleus unlike : side view in 7 and 2 
and polar view in /, where the open ends of the loops point towards the old equator. 
Finally the eta sae is constituted as in m and # side and surface (polar) 
views respectively. But as about to divide again, the return to the resting state 
is not complete, AE e a a continuous filament is established, with local thicken- 
ings on it, showing the chromatin already segmenting. While segmentation pro- 
ceeds, the segments get into the meridians and shorten towards the equator (f and g), 
then the spindle is formed (7), and after the anaphase straight rods of chromatin 
pass to the poles, where they curve into loops (s, 7). This series shows what varia- 
bility there may be between successive divisions of same nucleus. Such variability 
- 124). 
FIG. 123, a-gx. Spermatogenesis of Helix pomatia.—a, the nucleus, with a thin 
layer of protoplasm about oh forming the “sperm mother-cell.” It is now homogene- 
ous, soon becomes granular, and a reticulum is developed (4). Out of the nucleus 
now buds a paranucleus (x). Then there is a period of growth until we get c, with 
a rich surface reticulum of chromatin. In g the meshes of the reticulum 
absorbed by the TAS In e hiss —— a ie any a 
formed four microsomata ; these re distant 
distribution, and, by tie the connecting proteases in i aie s directii and 
strengthening them in a meridional direction, they form a series of loops of a filament 
e MIRER now approaches the pole, and at the same time the loops 
ikri towards it, forming a rosette (g). The outer turns of the rosette break, as 
seen in polar view given in 4. The paranucleus is absorbed, and the loops with their 
bends wa ea axis ssi saree to the dre cee (J); at a same — Sr SPEA is 
formed. 
such bodies in an cea sie (4); the fibres of the spindle are in union, by- 
means of the rays of the polar aster, with the cytoplasmic reticulum. Each karysoma 
now segments again into four microsomata (/), but only the first plane Lees in the 
meridian cuts through completely; the second is simply the beginning of an attempt 
_ to form a beaded filament. These short filaments, consisting each of a pair of mi- 
