KARYOKINESIS AND ITS RELATION TO FERTILIZATION. 257 
able difficulty to the doctrines of Minot, Balfour, and E. van 
Beneden. It is the simple fact, which it is astonishing that the 
authors concerned have not seen for themselves, of the trans- 
mission of male ancestral characters through the mother, as, 
for instance, is frequently exhibited by children inheriting pecu- 
liarities of their grandfather on their mother’s side. According 
to Minot, Balfour, and van Beneden this would be impossible, 
for the mother must have extruded as directive corpuscles from 
her egg-cells all constituents which had been received from her 
father. The upholders of the original bisexuality of the egg- 
cell must suppose that each time a small remnant remains 
behind ; but then there would be no sense at all in eliminating 
anything. By their theory, too, the second directive corpuscle 
receives no satisfactory explanation. 
In order to be as exhaustive as possible in regard to the 
directive corpuscles, I will yet mention the older theories 
which have dealt with the significance of these bodies. In 
earlier times they were simply regarded as excretory products 
which the egg got rid of in order to become as much purified 
as possible before fertilization. Then, some like O. Hertwig 
(1. c.), and others, such as v. Jhering (100), and Kélliker (108), 
regarded them as a means of removing the inequality in size 
between the germinal vesicle and the head of the spermatozoon. 
Whitman (206), with whom Flemming (61) agreed, regarded 
the process as a phylogenetic remnant of a parthenogenetic re- 
production by simple division of the egg-cell, which was present 
universally in our earlier ancestors. Biitschli’s view (48), 
which was maintained recently by O. Hertwig in his excellent 
‘ Lehrbuch der Entwicklungsgeschichte,’ as the most acceptable, 
depends on the following considerations :—For a long time past 
the conclusion has been established that developmentally a 
sperm mother-cell is the exact equivalent of a primary egg-cell. 
If we suppose, with Pfliiger (158), that the primary eggs can 
still divide, and that then the products of repeated division 
appear as the definitive eggs, which is not certain in all case, 
even then the number of divisions of a primary egg-cell is small 
in comparison with the number of divisions which a primary 
