604 Wisconsin Academy of Sciences, Arts, and Letters. 
most probable explanation of the latter was the side by side 
pairing of paternal and maternal chromosomes when in the 
thin spirem condition. 
Sutton in 1902 (,101) reported that the 22 ordinary chromo¬ 
somes of Brachystola magna could be separated into eleven 
pairs, each pair differing from the others as to size. Further, 
in the spermatids after reduction has taken place a graded series 
of eleven chromosomes can be seen showing that each germ cell 
has received one member of each of the eleven pairs. He 
found that the chromosomes of th© oogonia as well as those of 
the ovarian follicle cells corresponded with those of the sperma¬ 
togonia. The union of the male and female germ cells would 
therefore give 22 chromosomes, but only eleven different sizes, 
—or eleven different pairs. These results Sutton believes con¬ 
firm Montgomery’s conclusions as to the pairing and conjuga¬ 
tion of paternal and maternal chromosomes. 
As early as 1882 Strasburger reported a great dissimilarity 
in the size of the chromosomes of the pollen mother cells of 
Funkia Sieboldiana. Gruignard in 1899 called attention to 
the fact of chromosomes of different size in pollen mother cells 
of JSTaias major. Koernieke in 1901 also observed that in the 
embryo-sac of Yucca filamentosa, the chromosomes differed 
strikingly from one another. These observers did not at the 
time connect any particular significance with the described 
facts. 
In 1903 (104) de Vries advanced the view that th© parental 
chromosomes remain distinct through the diploid generation 
and at a period at the close of the sporophyte generation there 
must be an intimate association of the homologous chromo¬ 
somes, after which separation occurs. He assumed a side by 
side pairing as providing the best means for intimate asso¬ 
ciation, and believed that this association occurs previous to 
the separation of the halves of the heterotypic chromosomes. 
Rosenberg has reported (79) that in the embryo-sac mother 
cell of Listera ovata there are 32 somatic chromosomes of dis¬ 
similar sizes. These pair to formi the 16 bivalent heterotypic 
chromosomes of which five are strikingly larger than the re- 
