Chromosomes in Living Organisms. 297 
to so low a group as the Myxomycetes. I believe that the 
nuclei of Trickia fallax contain each twelve chromosomes: 
I counted them in my old preparations 1 showing numerous 
nuclear divisions in developing sporangia. It is true that the 
nuclei are so small that absolute accuracy in the counting 
is hardly attainable : still one cannot but be impressed by 
the remarkably uniform appearance of the nuclear divisions. 
If, however, the number of the chromosomes be constant in 
the Myxomycetes, there can be little doubt but that it is 
so universally: and then it becomes probable that a reduction 
in the number of the chromosomes must be associated with 
some definite developmental stage in those of these lower 
Cryptogams which are sexually differentiated. The assump- 
tion that this reduction takes place during the development 
of the sexual organs is not supported by any direct evidence, 
and it is contrary to what has been ascertained in the higher 
Cryptogams. It may be that the reduction follows the sexual 
act. In all these cases in which the original generation is 
directly developed from the product of fertilization, the re- 
duction probably takes place during germination : here the 
zygote is all that represents that developmental stage, the 
asexual generation, which intervenes in the Muscineae, the 
Pteridophyta, and the Phanerogams, between fertilization and 
formation of spore-mother-cells. On the other hand it is 
possible that, in Coleochaete , Oedogonium , or the Florideae, 
the reduction does not take place until the development of 
the, motile or non-motile, spores with which the product 
of the sexual act closes its existence ; for it is from these 
spores that the first generation is, in turn, developed. 
The constancy of the number of the chromosomes in the 
nuclei of the sexual cells is doubtless of great importance, 
for it ensures the equal influence of the two parents in the 
sexual act : and the act of fertilization is, in all the higher 
organisms, the centre of gravity of the maintenance and 
development of the species. In contrast with this is the 
1 Zur Entwicklungsgeschichte der Sporangien von Trichia fallax , Bot. Zeitg., 
1884, Taf. Ill, Fig. 6. 
X 2 
