1895.] Anatomical and Physiological Researches. 25 
While constancy in the number of chromosomes in the gen- 
erative nuclei is doubtless of great importance, there is no 
cells that are no longer embryonic, and especially in those 
definitively excluded from the sphere of reproduction (as the 
lower nucleus of the embryo-sac from which the antipodal 
cells are derived, and also the definitive nucleus which origin- 
ates the endosperm). Inthe prothallial nuclei of Pinus syl- 
vestris it has been observed that the reduced number is 
adhered to until the development of archegonia, and then it 
may be departed from, sometimes even doubling in the large 
nuclei of the wall-cells of the archegonia. 
In the case of apogamy among ferns it seems probable that 
the number is doubled on the development of the growing 
points of the sporophyte. In the case of apospory it seems 
probable that there is a corresponding reduction, or else the 
resulting prothallia must contain twice as many chromosomes 
as normally developed prothallia. 
The continuity of the chromosomes from generation to 
no such thing among plants as nuclear divisions resulting in 
the reduction of the number of chromosomes by one-half. 
It is also shown that there is no such thing as hereditarily 
unequal divisions in karyokinesis. The author believes thor- 
oughly in epigenesis, and that cell-nuclei, wherever in the 
body they may be, are and remain endowed with all the char- 
acteristics of the species and are stimulated to activity in defi- 
Hite directions by prevalent conditions. He approves of 
Weismann’s term « id,” as it represents something supported 
by direct observation. He would recognize as ids the serially 
arranged discoid segments of the chromosomes. These ids 
are repetitions of each other, and in the sexual act the chro- 
MOsomes of the parents do not lose their independence, but 
show various results in various parts dependent upon the in- 
teraction of the chromosomes giving rise to phenomena of 
‘nterference. In this way the various resemblances of hybrids 
