ON INDIAN OLIGOCU^TA. 103 



5. Contributions to the Morphology, Classification, and 

 Zoogeography of Indian Oligochseta. By J. Stephen- 

 son, D.Sc, F.Z.S., Lecturer in Zoology in the 

 University of Edinburgh. 



[Received Novembor 6, 1920 : Read February 22, 1921.] 



(Text-figure 1.) 



Contents. Page 



1. The Affinities and Systematic Position of the Geuus 103 

 Eudichogaster Mchlsii., and some related questions ... 



II. On Polyphyly in the 01igocha3ta 112 



III. Some general Considerations on the Geographical Distri- 

 bution of Indian Oligochieta 124 



I. — The Affinities and Systematic .Position of the Genus 



Ei'JJICUOGASTER MCHLSN., AND SOME RELATED QUESTIONS. 



The genus Eudichogaster was established in 1902 by Michael- 

 sen (2) for E. ashworthi, then first made known, and for several 

 other worms which had been originally described as species of 

 Dichogaster (or Benhatnia), but which were placed by Michaelsen 

 in the Tierreich volume of 1900 in the genus Trigaster. The 

 separation of these three genera is based on the presence or 

 absence and on the position of the calciferous glands ; Trigaster 

 has none, Eudichogaster has them in xi. and xii. (with, it may be, 

 X. or xiii. in addition), Dichogaster has them in xiv., xv. and xvi,, 

 or in XV., xvi. and xvii. The diagnosis of the genus Eudichogaster 

 is as follows : — 



Setse four pairs per segment. Prostatic pores two pairs on 

 xvii. and xix., or one pair on xvii. (? or xviii.). Spermathecal 

 poi-es two pairs on viii. and ix., or one pair on viii., or in groove 7/8. 

 Two gizzards in front of the testis segments. Calciferous glands 

 two or three pairs, in xi. and xii., or x., xi. and xii., or xi., xii. 

 and xiii. (in one species no proper calciferous glands recognizable). 

 Micronephridial. One or, more usually, two pairs of testes. 

 Prostates tubular. 



In the paper in which the genus was established, Michaelsen 

 placed it in the Trigastrinte. In 1903, however (3), he leans to 

 the view that it is to be derived from Octochcetics, and there- 

 fore to be included in the Octochsetinse, though he does not carry 

 out this implication in the tables. In 1909 (4) he definitely 

 adopts this view. In 1910 (5) he abandons it, and, deriving 

 Eudichogaster from IVigaster, again places it in the Trigastrinte. 

 The object of the present communication is, by bringing forward 

 additional evidence, to decide the question in favour of its 

 inclusion in the Octochajtinas, by showing that it is descended 

 from Octochcetus, not fi'om Trigaster. 



