13. In Metaphire the three kinds of nephridia are distributed as follows*

4 points

(a) All segments except 1st to 4th and 10th to 14th segments

(b) All segments except first three segments

(c) Meganephridia in pre-clitellar segments and micronephridia in post-clitellar segments

(d) Micronephridia in all segments, meganephridia in dlitellar and post-clitellar regions