Question

Distinguish between the following: 

1. Prostomium and peristomium 

2. Septal nephridium and pharyngeal nephridium

Answer 1

1. Prostomium is the front most part of the earth-worm. This is not called a true segment as it doesn’t contain typical organs of an annelida. Peristomium is from where the true segment of the earthworm body starts. 

2. Septal nephridia, present on both the sides of intersegmental septa of segment 15 to the last that open into intestine.

Pharyngeal nephridia, present as three paired tufts in the 4^th , 5^th and 6^th segments Both are same structurally and functionally.