235 
Pollen Mother -cells of Li Hum canadense . 
in the offspring is 16 , 777 , 216 . On the other hand, the reduced number of 
chromosomes in the pea, as Cannon (’03 b) finds, is seven ; and he has 
pointed out that on Sutton’s hypothesis there can be only seven groups of 
characters, each of which groups can be transmitted independently of any 
other. Now, Mendel found in varieties of the pea seven separate characters 
which were transmitted independently of each other ; and if Sutton’s notion 
be correct, each of these characters must be one of a set which corresponds 
to one of the indivisible chromosomes ; and Mendel could not possibly, 
therefore, have found an eighth character which would follow his law of the 
separation of parental qualities. To suppose that Mendel so completely 
exhausted the possibilities of the case is probably giving him more credit 
than even his most devoted followers would be inclined to allow. 
Montgomery’s notion, that any two chromosomes which conjugate in 
synapsis are derived respectively from the male and the female parents, was 
supported by his observation (’ 01 ) that when, as in Protenor , Peliopelta , and 
Zaitha , certain spermatogonial chromosomes are distinguishable from the 
others by their size, these peculiar chromosomes pair with each other in 
synapsis. A striking case of the same sort is furnished by Brachystola , 
according to Sutton (’02). Here all the spermatogonial chromosomes, as 
already mentioned, can be arranged according to their varying sizes in 
pairs ; and each bivalent heterotypic chromosome is formed by one of 
these pairs of hitherto separate elements. Similar phenomena to those 
found by Sutton are described by Montgomery (’04) for the spermato- 
genesis of Plethodon and Desmognathus , and for the oogenesis of Ascaris 
megalocephala bivalens. 
Hacker (’02, ’04) has observed phenomena in the oogenesis of 
Cyclops brevicornis y which he interprets as a conjugation of paternal and 
maternal chromosomes. In the germinal vesicle the bivalent chromosomes 
are arranged in two groups, representing respectively, he thinks, the maternal 
and paternal elements. The first maturation division is equational, so that 
the chromosomes passing to the secondary oocyte may be represented by 
ab , cd, . . . (male), and no : pq , . . . (female). In the secondary oocyte nucleus, 
a conjugation in pairs occurs between these chromosomes — e. g. ab (male), 
which is bent at its middle, comes into contact at the point of bending with 
the similarly bent no (female). In the second maturation division, a trans- 
verse division of each chromosome occurs at the point of bending, so that 
the separation in this division may be represented thus : 
a (male) n (female) 
I 1 
b (male) o (female) ..... 
There is thus effected a thorough mixing of the parental elements, 
and each germ-cell receives an equal number of chromosomes originally 
derived from each parent. 
S 
