STUDIES ON EARTHWORMS. PAKS 
Bourne was the first to figure them in their true position 
attached to the anterior septum of somites x and x1, as two 
pairs of small flat appendices. This figure and description occur 
in a paper by J. E. Blomfield (7), who describes the develop- 
ment of the spermatozoa in the reservoirs. 
The sperm ducts were rightly described by Leo (8) in 
1820, but Dugés (2) wrongly considered them as oviducts. 
The nephridia or ‘‘segmental organs” also were erro- 
neously interpreted by Dr. Williams in 1858 (40), being con- 
sidered as respiratory organs. Their true function was first 
suggested by d’Udekem (9) in his description of Tubifex, whilst 
Gegenbaur (10) in 1853 published the well-known drawing of 
this organ of Lumbricus agricola, the histological struc- 
ture of which was described by Claparéde (11). 
In regard to the classification of Earthworms, that of 
Claparéde (12) in 1862 is usually followed. He divides the 
order Oligocheta into two families, Limicolz and Terri- 
colz, but the characters of the latter, as opposed to the 
former, were derived from the genus Lumbricus only, and 
now, since the investigation of other genera, no longer hold 
‘true. These are his characters: 
a. The possession of two ventral blood-vessels. 
b. The presence of nephridia in the same somites with the 
sperm ducts and oviducts. 
c. The position of the clitellum far behind the male pores. 
d. The presence of a vascular network on the nephridia. 
Now, Perrier’s genus Pontodrilus (13) and Pericheta 
have no subneural blood-vessel [Microcheta! resembles 
these two genera in this respect], and very possibly others will 
also be found without this vessel. 
The position of the clitellum is now known to vary ; some- 
times it is in front, sometimes around as well as behind the 
male pore. 
The truly distinctive characters of the Terricolz (or 
Lumbricine, as Perrier calls them), as opposed to the 
Limicole, are the following : 
} Names or sentences in square brackets refer to results of my own research. 
