Spermatozoa were observed under conditions which did not spatially restrict their movements. They differed from each other in pattern of movement and velocity of progression. Movement patterns ranged from undulating, whirling or circling, to progression along helical paths varying from near circles to straight lines. Progression velocity varied over a wide range.
Progressing spermatozoa travelled predominantly downwards although gravity did not significantly effect velocity. A protoplasmic droplet on the midpiece was associated with lower average velocity. Average velocity was initially higher at high pH but the proportion of progressing spermatozoa decreased while whirling and circling movements increased. At low pH the average velocity was less but more spermatozoa progressed along relatively straight lines. They were observed to change from one movement pattern to another.
The range of activity patterns and the influence of physical conditions indicate that it is unwise to define 'normal' movements without further evidence.
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