Agglutination refers to the clumping together of sperm cells. This is common and prevents the sperm from being “viable”. I quote from the study Discussion: Much variation exists in these semen qualities between individuals and between samples. For this reason, the most rapid and dependable technique for identifying the scorbutic effect [what the vitamin C does, Rusty] on fertility in man is the microscopic measurement of sperm agglutination.
Here we see that both supplemented groups responded similarly and positively. And again we see significant improvement after only one week.