5 8o THE AMERICAN NATURALIST. (VoL. XXXIX. 
Rosenberg's (:04a, : 04b) studies on hybrids of Drosera rotun- 
difolia (with ten chromosomes in the gametophyte) and D. longi- 
folia (with twenty chromosomes) offer clear evidence that the 
chromosomes which unite in pairs to form bivalent structures 
preliminary to the reduction phenomena of sporogenesis are of 
different parentage. The sporophyte number of chromosomes 
in the hybrid is thirty, as would be expected. The reduced 
number appearing at the first mitosis of sporogenesis is, however, 
not fifteen but twenty chromosomes, ten of which are plainly 
double the size of the other ten. The explanation of this inter- 
esting condition is that the ten chromosomes of 2. rotundifolia 
unite with one half of the twenty chromosomes of D, longifolia 
giving ten large bivalent structures accompanied by the ten 
chromosomes of D. longifolia which are without mates. This 
explanation finds clear support in the facts that the chromo- 
somes of D. rotundifolia are larger than those of D. longifolia | 
and that the bivalent structure consists of a larger and a smaller 
element thus giving clear evidence that the pairs of chromosomes 
Which unite in Drosera are of different parentage. The single 
chromosomes which are without mates may pass to one or the 
other of the poles of the spindle or may be left behind when the 
daughter nuclei are formed. 
This group of investigations illustrates very clearly the charac- 
ter of the evidence that is leading many biologists to assign to 
the chromosomes the functions of bearing and distributing hered- 
itary characters. The question at once comes up as to whether 
or not the chromosomes may differ among themselves to a 
greater or less extent even in the same species or individual. 
Montgomery, Sutton, with others, have established a difference 
in the szze of chromosomes. Baumgartner distinguishes differ- 
ences in form in the same species and the studies of Moenkhaus 
and Rosenberg have shown that the chromosomes of different 
parents may retain their peculiarities of form in hybrids and be 
really separated. To these investigations should be added the 
recent conclusions of Boveri (102, :04), that chromosomes actu- 
ally differ in function. Boveri found that the chromosomes of 
eggs of echinoderms that were fertilized by two or more sperms 
are distributed by multipolar spindles to a varying number of 
