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No. 464.] STUDIES ON PLANT CELL.— VII. 581 
blastomeres which in consequence received a varying number 
and assortment of chromosomes. Boveri then separated these 
blastomeres and followed their independent development into 
larval stages which exhibited marked differences in form that 
could be correlated with the irregularities in the number of 
chromosomes contained in each, thus suggesting that specific 
chromosomes have specific functions. With this sort of evi- 
dence accumulating from both the morphological and physio- 
logical side it is not surprising that many biologists believe 
that specific characters are actually held or are controlled by 
chromosomes or groups of chromosomes. 
Such views of course presuppose that the chromosomes retain 
a high degree of independence of one another and that variation 
is expressed chiefly through different combinations of chromo- 
somes and not by modifications of the chromosomes themselves. 
Yet there is strong evidence of an actual mixing or interchange 
of the idioplasm among the chromosomes. This possibility 
"which is of course contradictory to the view of the complete 
independence of the chromosomes finds its chief support in the 
close association of the pairs of chromosomes with the organiza- 
tion of the reduced number of bivalent structures during synap- 
sis. These pairs have been reported so intimately united as to 
be actually fused. Allen (:05) has described for Lilium the 
union of two sets of chromomeres, one believed to be derived 
from a paternal spirem and the other from a maternal, which 
come to lie side by side during synapsis and unite to form a 
spirem with a single series of fusion chromomeres. This single 
(fusion) spirem later splits longitudinally and the two halves are 
regarded as again representing maternal and paternal spirems 
but there are evidently opportunities during the period of fusion 
for significant reciprocal interaction between the two idioplasms. 
This conception of the fusion of idioplasm from the two, parents 
is an old view which has been held by such well known biologists 
as Hertwig and Strasburger. ey 
De Vries (: 03) has recently discussed the significance of the 
pairing of chromosomes before the heterotypic mitosis in relation 
to the theory of pangenesis. He conceives the paternal and 
maternal chromosomes as coming together during synapsis in 
