310 



OLIGOCHAETA 



the position of the reproductive organs; the testes are in the eleventh segment'; 

 the ovaries in the following segment. The sperm-ducts open by a very reduced 

 spermiducal gland on to the twelfth segment ; the funnel of these ducts is peculiar 

 in form, being generally extremely long and of a glandular appearance ; the oviducts 

 are represented merely by pores ; or rather by a short prolongation of the septum 

 which meets the pore ; they seem to be degenerate. The spermathecae are far 

 forward opening on to the intersegmental furrow iv/v ; as a rule they open into 

 the gut, a fact which is paralleled in the genus Sutroa, and was first discovered in 

 the present family by Michablsen (14). Egg-sacs and sperm-sacs are only present 

 in Mesenchytraeus. The above characters distinguish the Enchytraeidae from all 

 other Oligochaeta. 



Michablsen allows twelve genera, of which two (not described by himself) must 

 be considered doubtful ; these genera are Ghirodrilus and Bistichopus ; I shall recur 

 to them presently. To these 'Bryodrilus of Ude (2), and Parenchytraeus of Hesse 

 must be added. 



The genera which appear to be valid may be thus distinguished : — 



Mbsektchtteaeus. 

 stebctjti7s. 

 Pachydbiltjs. 

 buchholzia. 



Hebtlea. 



ElJ-CHTTKAETJS. 

 FKIDEBICIA. 



AWACHAETA. 



Setae ./-shaped ; no dorsal pores, only a head-pore ; origin of 



dorsal vessel postclitellian, contains a glandular body. 

 Setae y-shaped ; origin of dorsal vessel anteclitellian, contains 



a glandular bodj'. 

 Setae ./-shaped ; no dorsal pores ; blood coloured ; dorsal vessel 



originates behind clitellum, contains no glandular body. 

 Setae y-shaped ; dorsal f)ores absent ; dorsal vessel originates 



from the tip of the single dorsal diverticulum of the gut ; 



salivary glands present. 

 Setae straight or /-shaped ; origin of dorsal vessel anteclitellian ; 



no dorsal pores ; oesophagus sharply marked off froin 



intestine. 

 Setae straight; dorsal vessel postclitellian in origin. 

 Setae straight ; dorsal pores present ; salivary glands present ; 



dorsal vessel postclitellian in origin. 

 No setae ; no dorsal pores ; dorsal vessel anteclitellian in 



origin ; a single salivary gland ; spermathecae not opening 



into gut. 



' In a few forms the testes, &c., are further forward. 



