AND ZOOGEOGRAPHi" OF INDIAN OLIGOCH^TA. 139 



in one place in the African, in another place in the Oriental 

 branch. There is therefore no question of African forms having 

 travelled to India, or of Indian forms to Africa ; the question is, 

 where did the common ancestor live ? We can only say, we do 

 not know. Smith and C4reen, the discoverers of the African 

 form, do indeed suppose this ancestor to have arisen somewhere 

 in Gondwanaland, whence the Syngenodriline branch migrated 

 to Africa, the Moniligastrine to the Oriental region (17) ; but 

 so far as I know there is no special reason for the supposition. 



Wallace, as is well known, gave up Lemuria, and became a 

 believer in the permanence of the ocean basins. Matthew states 

 that there is no necessity for Gondwana, from a pala?ontologica.l 

 point of view — not even in the Palaeozoic, if the interjjretation of 

 the facts of distribution is made along the lines he lays down 

 (origin of groups in the north, spread towards the south, the 

 more primitive groups first and furthest) ; the weakness of the 

 original evidence for the former existence of Gondwana is 

 forgotten, and new discoveries are interpreted in the light of it, 

 as if its existence were well established. 



The A.merico-African bridge, from Central America to tropical 

 Africa, does not concern us so closely, and in showing reason to 

 believe that EudicJiogaster originated in India, we entirely do 

 away with the necessity for it so far as India is concerned. 

 Whether the large number of African Dichogasters can be 

 explained as easily as the large number of Indian and far Eastern 

 species of this genus — as having been carried to their new homes 

 in the way of trade or human intercourse — seems doubtful. At 

 the same time, in assuming a land-bridge we are probably getting 

 more than we ask for ; what we want is a passage for the extremely 

 slow-moving earthworms, and when it is a matter of thousands 

 of miles this passage must be one of some permanency ; what we 

 actually get, therefore, is an easy and abundant passage, for a 

 long space of time, for all the elements of the fauna, and a 

 mingling of the animals of the two regions to an extent Avhich 

 has certainly never happened. I can only conclude that we are 

 probably better off, on the whole, without the Americo-African 

 bridge. 



The objections to the Indo- Australian and Indo-New Zealand 

 bridges have already been sufficiently insisted on. And not only 

 are the objections more striking than elsewhere, but — at least in 

 the case of the Australian bridge — the difficulty in dispensing with 

 the connection is also smaller. The actual distance to be accounted 

 for, as is Avell known, is not great. A union of the eastern part 

 of the Malay Archipelago with Australia, and of the western part 

 Avith Further India, is not only a feasible but a necessary suppo- 

 sition on every ground ; a land-bridge spanning the interval 

 between the eastern and western parts of the Archipelago is 

 objectionable except for the specific purpose of accounting for the 

 distribution of the Oligochseta. Wallace placed the boundary 

 between the two dissimilar faunas of the Australian and Oriental 



