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



regions between the islands of Bali and Lombok; this is the 

 interval where the assumption of a land-bridge raises many more 

 difficulties than it explains. But the interval is only fifteen miles ; 

 and while birds' feet and natural rafts offer a sufficient mode of 

 transfer for worms and their cocoons, they cannot serve to trans- 

 plant the mammals — not a whole mammalian fauna at any rate. 

 It is, too, in the genera of the Megascolecinae, the group which is 

 common to India and Australia, that we have seen most reason 

 to believe in polyphyletic origins ; as bearing on the probability 

 of polyphyly it is interesting to recall what Michaelsen says (7). 

 concerning the broad differences between the Indian and 

 Australian groups of MegascoJex — that the Australian species are 

 simpler, at a lower level of evolution, and more uniform, while 

 the Ceylonese species are often further advanced and in many 

 cases approach Pheretima. We can thus manage quite Avell with 

 the verte causae we know, but the bridge would only embarrass us. 



The distance to be overcome in the case of ISIew Zealand is 

 greater ; but the general faunistic objections to a land connection 

 with tS.W. Asia (which is supposed to have avoided Australia.) 

 are greater also. We are compelled, therefore, to invoke the same 

 agencies as before. 



Michaelsen's plea for a bridge across the Bay of Bengal, by 

 which worms from Australia, and also from Further India, could 

 reach the south of the peninsula and Ceylon without going round 

 by the head of the Bay, depends for its force on the presence in 

 S. India and Ceylon of genera which are not found elsewhere in 

 India, ; the argument is that if these genera had passed through 

 the lands about the head of the Bay, they would have left there 

 some trace of their passage. Thus Drawida, a Moniligastrid, 

 common in S. India, and descended from a form which was 

 probably not unlike Desmogasier (now found in Burma,, Sumatra, 

 and Borneo), was, when Michaelsen wrote, unknown from the 

 intervening region, except for a few records of peregrine species. 

 But more recent discoveries have shown that, both in the E. 

 Himalayas and near the coast at the head of the Bay, there are 

 a number of endemic species of Drawida ; and it can no longer 

 be urged that the Moniligastridae cannot have passed round that 

 way because they have left no trace of their passage. Certain 

 genera of the Megascolecinae also were supposed to show the same 

 limitation of distribution. JSfotoscolex was only known from 

 S. India and Ceylon, and the same was true of its descendant 

 Meqascolex. Lately, however, the E. Himalayas have been shown 

 to harbour three species (and a variety) of J\ r otoscolex (Megascolides 

 oneilli is a Notoscolex) ; so that here again it can no longer be 

 claimed that a bridge across the Bay of Bengal is necessary because 

 otherwise the genus would have left some trace of its passage 

 round the head of the Bay. And the polyphyletic origin of 

 Megasaolex is, I think, clear enough to allow us to dispense with 

 the supposition that it migrated into India from outside, whether 

 round the head of the Bay or by a land-bridge across it. 



