Number of lateral hearts in Pheretima are

In $Pheretima$,there are red-colored round bodies present above the alimentary canal in the $4^{th}$,$5^{th}$,and $6^{th}$ segments. It is believed that they are involved in:

In earthworms,spermatogenesis occurs in the ..........

Define the following terms:
$(i)$ Endomysium
$(ii)$ Prostomium

$A$ characteristic feature of the earthworm,$Pheretima$,is that:

In earthworm,fertilization occurs in