134 Proceedings of the Royal Physical Society. 
Fol, v. Beneden, Boveri, Guignard, and others! have 
established, for both animal and vegetable cells, the fact, 
that during fecundation the paternal and maternal attractive 
spheres play an important role, especially in bringing about 
an equal division of the two sets of organs derived from the 
father and mother respectively. How this is possible we 
may learn from the observations of Fol and Guignard, who 
found that a union of paternal and maternal attractive 
spheres takes place during fecundation. Given then, firstly, 
a set of “male” and “female” attractive spheres; secondly, 
an affinity of each sphere for its own male or female 
nuclear elements; thirdly, a union (not fusion !) of the two 
sets of spheres derived from the sperm and ovum; fourthly, 
a division of the newly-formed sphere (“zygote sphere”) in 
such a way that each daughter-sphere receives its share of 
maternal and paternal elements,—it then follows that on 
division of the “zygote” nucleus (Furchungskern, Hertwig), 
formed by the fusion of the paternal and maternal half nuclei 
(demi-nuclei), the nuclear segments will be divided in an 
equal manner between the two daughter-attractive spheres. 
I need hardly mention that the distribution of the nuclear 
segments will take place in quite an analogous manner in 
those cases where the two demi-nuclei do not pass through 
the stage of a “zygote” nucleus, but where they participate 
at once in the formation of the first division spindle 
(Furchungsspindel, Hertwig), as, eg., in Ascaris megalo- 
cephala. But to this different behaviour of the sperm and 
egg demi-nuclei I have to return afterwards, for as yet I 
have spoken of demi-nuclei without explaining how they 
arise. 
In animals and plants, in the lowest as well as the highest, 
we find that cells which are going to become sexual cells, 
pass through a certain stage, after which they will give rise, 
by a thrice repeated division, to eight sexual cells, and there- 
fore we may call this stage that of the grandmother-cells. 
If, now, a grandmother-cell possesses a nucleus with four 
chromatin segments, these are found to split longitudinally, 
and thus to form eight segments, four of which go to either 
1 For Literature, vide my paper on the Embryo-sac of Myosurus, ete. 
