109 
are closely packed, and are so numerous that counting is impossi- 
ble. In the early stages, however (Figs. 8 and 10), it can be seen 
that the number is about sixty. 
The compact arrangement of the tetrads in the nuclear plate 
leaves no chance for orientation. It is impossible, therefore, to 
tell from this division whether the tetrad divides through the line 
of original cleavage, or through the secondarily acquired trans- 
verse cleavage. In other words, it is impossible to tell whether 
the division of the primary sporocyte is a reducing or an equation 
division. There is, however, good reason to regard this as an 
equation division, and the division of the secondary sporocyte as 
transverse, and, therefore, as a reducing division. The second 
mitosis follows closely on the first, but in the short interval the 
two parts of each dyad, which at first appear like two small balls 
closely pressed together (Figs. 12 and 21), now become drawn out 
in the direction of their common axis, which is probably the 
original longitudinal axis of the spireme-segment (Figs. 13 and 
14). It is immaterial in the final spore cells whether the first or 
the second division is a reducing division in the Weismann sense. 
That one of them must be is shown by the method of tetrad 
formation; but, from the manner in which the dyads elongate, the 
probability is certainly strong that reduction is effected by the 
second mitosis. The change in shape of the chromosomes in the 
secondary sporocyte-spindle makes the general appearance of the 
nuclear plate conform more nearly with that of the somatic cells 
(cf. Figs. 13 and 18), although they are fundamentally different. 
4. The spore. 
The cylindrical shape of the daughter chromosomes as they 
come from the division of the dvads in the secondary sporocytes 
is retained until late in the anaphase (Fig. 14). The resulting 
four daughter-nuclei lie freely in a single cell which, until the cell- 
plates are formed, is a syncytium. In the division of multinuclear 
cells it has been frequently noted that the nuclei are connected by 
spindle fibres. This occurs in ferns, and long after division, and 
-even as late as the telophase after the cell-plates are formed and 
the nuclei have gone into the resting stage, fibres can still be seen 
connecting each nucleus with all the others (Figs. 14 and I 5). 
While the cell-plates are forming, the chromosomes gradually dis- 
