112 DR. J. STEPHENSON ON THE MORPHOLOGY, CLASSIFICATION, 



References to Literature. 



1. Mtchaelsen, W. — Oligochaeta, in : Das Tierreich. Berlin, 1900. 



2. „ Neue Oligochaeten und neueFundortealt-bekannter. Mitth. 



Naturhist. Mus. Hamburg, vol. xix. 1902. 

 3 „ Die geographische Verbreitung der Oligochaten. Berlin, 



1903. 



4. „ The Oligochseta of India, Nepal, Ceylon, Burma, and the 



Andaman Islands. Mem. Ind, Mus., vol. i. 1909. 



5. „ Die Oligochaten-fauna der vorderindisch - ceyloniscben 



Region. Abh. Naturw. Verein Hamburg, vol. xix, 1910. 



6. ,, Oligochaten, in : Ergebnisse der zweiten deutschen Zentral- 



Afrika-Expedition 1910-1911. Leipzig, 1915. 



7. Stephenson, J.— On a collection of Oligochgeta mainly from Northern India. 



Rec. Ind. Mus., vol. x. 1914. 



8. ,, On some Indian Oligocbaita, mainly from Southern India 



and Ceylon. Mom. Ind. Mus., vol. vi. 1915. 



9. ; , On a collection of OligochaHa belonging to the Indian 



Museum. Rec. Ind. Mus., vol. xii. 1916. 

 10. ,, On a collection of Oligochasta from various parts of India 



and Further India. Rec. Ind. Mus., vol. xiii. 1917. 

 ]_]_. On a collection of Oligocha'ta from the lesser known parts of 



India and from Eastern Persia. Mem. Ind. Mus., vol. vii. 



1920. 



II. — On Polyphyly in the Oligoch^eta. 



The material which I wish to use in this discussion is derived 

 from the Megascolecidse, and largely from the subfamily Mega- 

 scolecinaB. It will be necessary first to show how the various 

 genera of this subfamily are related (v. text-fig. 1). 



The whole of the family Megascolecida? is to be derived from 

 an original form which has essentially the characters of the genus 

 Notiodrilus as defined by Micbaelsen in the Tierreich volume of 

 1900. These are: Testes and funnels two pairs, free in seg- 

 ments x. and xi. ; vasa deferentia of each side uniting in their 

 backward course so that there is only one pair of male apertures, 

 on xviii. ; two pail's of tubular prostates, with unbranched central 

 canal, opening on xvii. and xix. ; setaj four pairs per segment ; 

 one pair of meganephridia per segment; a single gizzard far 

 forward, in segment v. or vi. 



The Megascolecinae, however, take their origin from a form 

 which is one remove from this — Diplotrema, in which the anterior 

 pair of prostates have disappeared and the posterior pair of 

 prostatic pores have moved forwards to open on xviii. near the 

 apertures of the vasa deferentia. 



In Phctelhis, the first genus of the Megascolecinte, the prostatic 

 pores have fused with the openings of the vasa deferentia on 

 xviii. so that there is but one pair of pores; and this remains 

 throughout the subfamily as its distinguishing character. In the 

 remaining genera the changes are of three chief kinds — the setae 

 may take on the perichsetine arrangement, the four pairs multiply 

 in number and become spread out to form a more or less com- 

 plete lina; round each segment ; the nephridia maybe broken up, 



