Antheridium is similar to Archegonium in all of the following except The chromosomal set
Their site on the gametophyte is convergent
Number of the gametes produced by each one
Type of division in each one

Explanation:

An archegonium (pl: archegonia), from the ancient Greek ἀρχή ("beginning") and γόνος ("offspring"), is a multicellular structure or organ of the gametophyte phase of certain plants, producing and containing the ovum or female gamete. The corresponding male organ is called the antheridium.

because photosynthesis could not occur (apex)