Assertion: semen's sperm | /r/HasAspect | head
Facets:
Source sentences:
text: If sperm have a double tail, no tail, or a head that is crooked, misshapen, has double heads, or too large, it is considered abnormal, and unable to successfully penetrate an egg.
text: Some sperm have two heads or two tails and if the testes are too warm they may die or spermatogenesis may not occur.