544 Lewis . — The Behaviour of the Chromosomes 
generally agreed that they are separate, distinct entities which persist in 
their individuality from cell generation to generation. 
Although Rabl (’85) was the first to attribute to the chromosomes the 
property of individuality, Boveri (’08) first formulated the hypothesis which 
has had such far-reaching influence on all subsequent work in cytology. 
While Boveri’s hypothesis was not accepted without reserve by all investi- 
gators, it has been quite generally adhered to, and it is only just recently 
that it has again been brought seriously into question. Recent research has 
caused a growing belief that too much speculation has been based on the 
theory of the individuality of the chromosomes. 
All work of the past which has been done in support of the hypothesis 
has endeavoured to show that the chromosomes are capable of a complete 
re-formation after having first entirely lost their identity in the resting nucleus. 
The researches of Herla (’93), Haecker ('95), Moenkhaus (’04), Ruckert (’04), 
Zoga (’95) and others furnish us with abundant evidence that the maternal 
and paternal chromatin remain distinct from each other for at least several 
divisions in the developing embryo. Ruckert has also shown that the 
chromatin of the germinal vesicle appears in two distinct groups, and he 
suggests as possible that these groups may represent the maternal and 
paternal elements which have remained distinct throughout the entire life of 
the organism down to the formation of the egg. It has been shown for 
Pinus by Miss Ferguson (’04), Blackman (’98), Chamberlain (’04), and 
others that the gamete- nuclei do not unite at fecundation and that the 
chromosomes of the first cleavage division of the egg appear in two groups. 
Blackman (’04) and others have shown that the two nuclei in the Uridineae 
do not fuse for many generations after their association in the same cell, 
in fact not until the close of the life cycle—the meiotic phase. 
Moenkhaus (’04) showed that the chromosomes actually remain distinct 
in a certain hybrid fish until the third division of the embryo. Probably 
the strongest argument in favour of the persistence of the chromosomes 
from generation to generation as distinct morphological identities is to be 
found in the report of Rosenberg (’04) for Drosera hybrids. This writer 
has shown that in the hybrid sporophyte produced by crossing Drosera 
rotundifolia with D. longifolia , which have respectively ten and twenty 
chromosomes, the chromosome number is thirty as would be expected. 
At the time of the next succeeding reduction division, however, the number 
is not fifteen bivalents as would be found ordinarily after normal fecundation, 
but ten bivalents and ten univalents. Since the chromosomes of the two 
original species differ in both form and size, it is possible to recognize the 
chromosomes of the maternal and paternal ancestry. It is found, therefore, 
that the ten bivalents are formed of one from each ancestry respectively, 
and that the ten univalents are the ten from the one ancestry which did not 
find mates in the other group. This evidence seems to point conclusively 
