A complex network, however, does occur in Lybiodrilus and certain other Eudrilidae, where the paired nephridia possess ducts leading to the exterior which ramify and anastomose on the thickness of the body wall.
Lastly, towards the caudal region the right and left strands approach and anastomose, eventually coalescing in the mid line.
To adopt a figure, it is probable that the sources from which the two streams of life - animal and vegetable - spring may not be separable by a well-defined watershed at all, but consist of a great level upland, in which the waterways anastomose.