Memoirs: The Enteronephric Type of Nephridial System in the Genus Tonoscolex (Gates)

1. The ‘enteronephric’ type of nephridial system, previously described by the author in Pheretima, Lampito, and Woodwardiella (Nellogaster), has now been shown to characterize the genus Tonoscolex as well. It seems that this type of excretory system is widely distributed in the subfamily Megascolecinae. 2. The nephridia are of three kinds: the enteronephric septal nephridia, the exonephric integumentary nephridia, and the enteroriephric pharyngeal nephridia. There are twenty-four to thirty septal nephridia in each of those segments where they are best developed, these nephridia being much larger in size than the septal ruicronephridia of Pheretima. The pharyngeal nephridia form a cylindrical bunch around the oesophagus in the sixth segment and open into the pharynx in front by a large number of ducts. The integumentary nephridia are extremely minute and open singly on the body-wall. 3. The elaborate system of septal excretory canals and supraintestinal ducts characteristic of the septal nephridial systems of Pheretima, Lampito, and Woodwardiella, does not exist in Tonoscolex. The system in Tonoscolex is therefore much simpler and probably more primitive, and may represent an intermediate stage between the purely exonephric rneganephridia of Lumbricus and the elaborate enteronephric system of Pheretima, Lampito, and Woodwardiella.