The individual antheridia are sunk in depressions from which the spermatozoids are in some cases forcibly ejected.
"Encyclopaedia Britannica, 11th Edition, Volume 4, Part 3" by Various
It is called an "antheridium," and within are produced, by internal division, numerous excessively small spermatozoids.
"Elements of Structural and Systematic Botany" by Douglas Houghton Campbell
The egg and the spermatozoid both consist of protoplasm containing a nucleus.
"The Sexual Question" by August Forel
It is sometimes called spermatozoid; the plural is spermatozoa.
"Homo-culture" by Martin Luther Holbrook
Spermatozoids from G of fig.
"Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 7" by Various