SIGNIFICANCE OF THE SEXUAL PROCESS. 49 
From our present state of knowledge of the development of the 
blepharoplast there is but one conclusion, it seems to the author, that 
can be legitimately drawn concerning their origin, namely, that they 
arise de xovo. As regards centrosomes the evidence is more compli- 
cated and conflicting. Although, in the opinion of the author, the 
evidence is decidedly against the doctrine of the genetic continuity of 
the centrosome, yet the proof is not quite conclusive. If centrosomes 
also arise de xovo, then the problem assumes a slightly different aspect, 
for it is questionable whether we are justified in speaking of homologies 
between organs that, as such, are without genetic continuity. 
There is strong evidence, which seems to be increasing from day 
to day, that it is the fundamental substance known in the plant cell as 
kinoplasm which is genetically continuous. After a careful considera- 
tion of the facts, the author is led to the same conclusion concerning 
the centrosome to which he gave expression in 1900, in a paper on 
the nuclear division in Dzctyota (1. c., p. 178), namely, that it is the 
kinoplasm which should hold the rank of morphological unit, and that 
the centrosome should be regarded as an individualized part of the 
same, existing in that form in some organisms and not in others, for 
reasons that cannot at present be explained. As regards blepharo- 
plasts, about the only conclusion in harmony with all the facts is that 
these bodies represent individualized parts of the kinoplasm which 
arise de movo in certain spermagenous cells, and from which the cilia 
are developed. 
SIGNIFICANCE OF THE SEXUAL PROCESS AND THE NUMERI- 
CAL REDUCTION OF THE CHROMOSOMES. 
Speaking generally, the phenomena resulting from the sexual process 
fall into two categories, namely, (1) the transmission of hereditary 
characters, together with the blending of two lines of descent by the 
fusion of the sexual nuclei, and (2) the imparting of a growth stimulus 
to the fecundated egg or to the zygote, by which the energy of growth 
and division is restored. 
Correlative with the first category is the reduction in the number of 
chromosomes. The doctrine of the significance of the numerical 
reduction of the chromosomes now generally accepted by botanists as 
a working hypothesis, was first stated in a well organized form and 
presented formally to botanical science by Strasburger (’94) in a mas- 
terly essay on the ‘‘ Periodic Reduction of Chromosomes in Living 
Organisms.” The enunciation of this doctrine marked the beginning 
of a new epoch in the study of sexuality and in cytological research in 
plants. 
