16 Recent Work on the Reduction Division in Plants. 
considering the number of chromosomes many plants possess, the 
number of possible combinations of characters transmitted by the 
germ cells must be exceedingly great. Probably, too, the chromo¬ 
somes themselves are very elaborate structures. “ The smallest 
visible chromative granules may themselves well possess an 
inconceivably complex structure ; and it is not yet practicable to 
attempt to identify the lowest observable order of elements in the 
spirem-thread as the bearers of the apparently simple unit qualities 
manifested by the organism.” Strasburger thinks that the 
yellowness or greenness of the yellow or green pea depends on a 
single “ pangene ” (one of the ultimate units of which the chromo¬ 
somes are built up) but he considers it unlikely that the sole task 
of any pangene would be to determine the colour of the cotyledons, 
and is inclined to think that from each such pangene in the course 
of development of the organism a whole series of impulses would 
arise. The idea that certain definite pangenes are always associated 
together in one chromosome enables us to form a reasonable 
mental picture of a physical basis for “ correlation ” of apparently 
unrelated characters. 
Wager, 1 who lays great stress on the function of the nucleolus 
in storing chromatin and supplying it to the chromosomes, claims 
that the nucleolus must be considered in any future attempt to 
discover a cytological basis for the laws of heredity. But this 
seems to me to be founded on a misconception. When we speak 
of the “ individuality ” of the chromosomes, their “ permanence,” 
and the presence in them of definite pangenes determining certain 
characters, we do not of course mean that the chromosome is a 
stationary structure which persists as such throughout the life of 
the plant. It is clearly not so, for in the resting nucleus it is no 
longer visible in its characteristic condensed rod-like form. The 
thing that we conceive of as really permanent, in the sense that it 
is able to reproduce itself in each division, is the arrangement of 
the ultimate particles in each chromosome, and their relation to 
one another. Any given homologous pair of chromosomes 
appearing in the reduction division is “ identical ” with the 
corresponding chromosomes occurring in the previous egg and 
sperm nuclei only in the sense in which we use the word when we 
say that our present day selves are identical with ourselves of ten 
years ago. We feel a moral conviction that our identity is carried 
1 H. Wager. “The Nucleolus and Nuclear Division in the Root- 
Apex of Pliaseolus.” Annals of Hot. 19C4. 
