SEED-BEARING PLANTS 405 
bumping against each other and the wall of the tube in 
their reckless haste. They seldom escape from the upper 
cut end of the pollen-tube, although they as frequently 
swim toward this end of the tube as the other end, so far 
as could be observed. In many cases the pollen-tubes 
were cut so that the spermatozoids escaped into the solu- 
tion, and in numerous other cases mature turgid tubes 
burst in the process of cutting, discharging the uninjured 
spermatozoids in the sugar solution. The writer was 
thus able in many cases to study the spermatozoids swim- 
ming free and observe their unobstructed motion. 
"The motion of the spermatozoids when swimming free 
in sugar solution is in no way different from their motion 
when in the pollen-tube. The general motion is a con- 
tinuous rotation of the body, always in the same direction, 
around an axis passing through the apex of the helicoid 
spiral. Viewed from the head end or apex of the spiral 
the rotation is in the direction of the hands of a clock, and 
contrary to the turns of the spiral band. They roll 
around, first here, then there, resembling in this respect 
the motion of Pandorina. After moving about rapidly 
for from five to fifteen minutes they usually cease all pro- 
gressive motion, but continue to rotate for a considerably 
longer period. The rotary motion also soon ceases, but the 
cilia continue to vibrate for a considreably longer time. 
The spermatozoids of Zamia also have an amoeboid mo- 
tion, which is particularly noticeable while they are in- 
closed in the pollen-tube. The apex of the spiral as a 
whole frequently rotates in a most remarkable way, 
turning in a circle, pushing out first this way and then that 
way with the greatest freedom of motion, as if selecting a 
point of exit or ingress. In other cases the base or the side 
