Although this is almost impossible to demonstrate, there are probably as many filaments in the nuclear spindle as there are segments (in this case about sixteen), and along these the nuclear segments travel slowly toward the two poles of the spindle (Fig. 128, _A_, _B_). As the two sets of segments separate, they are seen to be connected by very numerous, delicate threads, and about the time the young nuclei reach the poles of the nuclear spindle, the first trace of the division wall appears in the form of isolated particles (microsomes), which arise first as thickenings of these threads in the middle of the cell, and appear in profile as a line of small granules not at first extending across the cell, but later, reaching completely across it (Fig. 128, _C_, _E_). These granules constitute the young cell wall or "cell plate," and finally coalesce to form a continuous membrane (Fig. 128, _F_). The two daughter nuclei pass through the same changes, but in reverse order that we saw in the mother nucleus previous to the formation of the nuclear plate, and by the time the partition wall is complete the nuclei have practically the same structure as the first stages we examined (Fig. 128, _F_).[15] [15] The division is repeated in the same way in each cell so that ultimately four pollen spores are formed from each of the original mother cells. This complicated process of nuclear division is known technically as "karyokinesis," and is found throughout the higher animals as well as plants.