74 JOSE F. NONIDEZ 
In all the individuals studied the spermatogonial metaphases 
contained normally thirty-five chromosomes (figs. 16 to 20). 
Three of them are readily identified on account of their large 
size and peculiar shape, as they almost always appear as curved, 
V-shaped rods, rarely straight or slightly bent, the arms of the V 
being of unequal length. Although their position in the meta- 
phase is variable it is commonly peripheral. 
It has been possible to find a correspondence in shape and size 
between two of the large chromosomes (figs. 16 to 20, M, M’), 
while the third chromosome differs from them in both shape and 
size. The latter was identified in my former papers as the ac- 
cessory or X-chromosome. ‘The paired large chromosomes were 
first termed ‘chromosomes a and b’ (14, p. 36) and subsequently 
“‘macrochromosomes’ or more simply, ‘M-chromosomes’ (’15, p. 
150), which name I will use in the present paper. 
In spite of some variation in shape and size in the large chromo- 
somes, found even in the same individual (fig. 21), the differences 
- mentioned above are almost always present. Furthermore, their 
mode of attachment to the spindle fibers, better seen in the early 
anaphase (figs. 23 to 27), strengthens this view. While the at- 
tachment is telomitic (Carothers, 717) for all the small chromo- 
somes (fig. 27), it is clearly atelomitic for the large ones, but a 
difference is perceptible in the latter: the M-chromosomes pos- 
sess a submedian attachment, while that of the X-chromosome 
is subterminal or nearly so. These conditions are already de- 
tected in the equatorial plate, as shown by the bending of the 
rod, except when the chromosomes appear as straight or slightly 
curved rods (fig. 21 a, c, d, e), in which case it is very difficult to 
ascertain the point of attachment of the fiber. No telomitic 
attachment in these chromosomes was ever found; it seems quite 
possible that the bending may appear when the spindle fibers 
being to pull the two halves apart. 
The small chromosomes appear as oval or elliptical bodies 
which have no constant position in the metaphase. In normal 
cells their number is thirty-two, but occasionally one or two 
more, or fewer may appear. In the first case this is probably 
due to their fragmentation; in the second to clumping. On the 
