On the Occurrence of the ‘Enteronephric’ Type of Nephridial System in Earthworms of the Genus Lampito

Abstract

ABSTRACT The ‘enteronephric’ type of nephridial system previously discovered by the author in the genus Pheretima has now been shown to be present in the genus Lampito also. The present investigation extends the distribution of this new type of excretory system and makes it probable that it occurs in other genera as well. In essential the nephridial system of Lampito agrees with that of Pheretima previously described; but while in Pheretima the ‘enteronephric’ nephridia are minute and multiple and have been described as micronephridia, these nephridia in Lampito are large and paired in each segment and are described as meganephridia. There are three distinct kinds of nephridia in Lampito, namely the septal, the pharyngeal, and the integumentary; of these, the septal ones communicate with the lumen of the gut through an elaborate system of ducts, the pharyngeal tufts of nephridia open into the pharyngeal cavity through bundles of ductules, while the integumentarios open on the skin individually through separate nephridiopores. The septal nephridia of Lampito resembles those of Lumbricus in their shape and disposition, but in their place of opening they agree with the enteronephridia of Pheretima. Therefore both micronephridia (Pheretima) and meganephridia (Lampito) can be ‘enteronephric’. Since there is no anatomical difference between micro- and meganephridia but only a difference in size, this classification of nephridia should be abolished. A better system is to classify them according to their place of opening and recognize ‘exonephric’ and ‘enteronephric’ types of nephridia, and amongst each of these types to distinguish between those that have an open internal funnel and those in which the internal end is closed. The septal nephridia of Lampito are characterized by the presence of multiple funnels to a single nephridium, and since in some species all the funnels are functional and in others one is functional and the others vestigial, it is suggested that the branching of funnels is a stage leading later to the multiple nephridia of Pheretima. Close similarity in their nephridial and other systems suggests a genetic relationship between the two genera Lampito and Pheretima, and the suggestion is supported by facts of geographical distribution of the two genera. Lampito provides a connecting link between Megascolex and Pheretima.