igoS,] W. MiCHAEivSEN : Oligochœta of the Indian Empire and Ceylon. 123 



Bengal. Outside of this dominion different species of Octochœtus are found only in 

 New Zealand. Neither Australia nor any other country or island intermediate between 

 these far distant districts presents any- Octochœtus. From Octochœtus was derived the 

 small genus Dinodrilus, found till now only in New Zealand, and from Dinodrilus was 

 derived Hoplochœtella, a small genus found, as well as Octochœtus, only in New Zealand 

 and India. The single Indian species of this genus lives in the southern part of the 

 Octochœtus district, namely in the Shevaroi Hills. From Octochœtus was derived as a 

 second branch the large genus Eutyphoeus (fig. vii in the text). This occupies with a 

 great number of species (seventeen or eighteen endemic and some peregrine in a very 

 small degree) the north-eastern part of India, the whole of the Himalayas as far as they 

 have been explored (the extreme eastern part of this chain of mountains is still unex- 

 plored) and a small district at its southern base, including almost the whole Prov- 

 ince of Bengal. A single isolated, apparently endemic species, probably an outpost 

 of this genus, is found in Burma (Rangoon). Outside of this dominion no Eutyphoeus 

 has been found. It therefore appears as if this genus took its full development in 

 this district, having been derived from that part of the genus Octochœtus which first 

 occupied the Indian dominion, which even now in one part in Bengal is identical 

 with a part of the Eutyphoeus district. 



We here have then a similar fact as in the distribution of the Megascolecine group 

 Perionychella, Perionyx and Lampito, as the oldest genus shows relations to far distant 

 regions, whilst a younger genus {Eutyphoeus) has made its development in the Indian 

 region alone. But the sub-family Octochœtinœ represents an outward geographical 

 relation quite different from those we observed in other families and sub-families, and 

 in this it differs also from the Perionychella-group. 



The Octochœtinœ represent a relation of the Indian region to New Zea. 

 land alone, not touching Australia. 



I have to mention here another relation of the Octochœtinœ which, it is true, is a 

 somewhat questionable one. The genus Howascolex from Madagascar, somewhat 

 provisionally placed within the sub-family Acanthodrilinœ, seems to be allied to the 

 Octochœtinœ. Perhaps it must even be regarded as the intermediate link between 

 these two sub-families, that is between Eodrilus and Octochœtus. It would be 

 difiScult to state whether Howascolex represented a geographical relation of Madagas- 

 car to New Zealand or to India. 



The phyletic relation of the sub-family Trigastrinœ (fig. viii in the text) to the 

 sub-family Octochœtinœ has not been completely cleared.^ Perhaps Eudichogaster is 

 the oldest trigastrine genus and was directly derived from the octochœtine genus 

 Octochœtus by a duplicating of the gizzard. From Eudichogaster the large genus 

 Dichogaster may be derived by a dislocation of the calciferous glands backwards. 

 Eudichogaster is found only in the north-western part of India ; this being just that 

 part of the country which has been left free by the genus Octochœtus. It almost seems 

 as though the conjectured octochaetine ancestor completely changed to Eudichogaster 



I See W. MICHAELS^N, Die geographische Verbreitung der Oligochœten, Berlin, 1903, p. 106. 



