164 OLIGOCHAETA 



Peripatus ; so, too, are the Struthious birds, the marsupials, &c. There are but few 

 Oligochaeta which fulfil this condition, and arguments based upon it would be 

 unsafe; still it may be worth while to point out, without laying too much stress 

 upon the facts, that Moniligaster found in India and the Bahamas is an example ; 

 perhaps, too, Ocnerodrilus is one; the genus occurs in the West Indies, South and 

 Central America on the one hand, and in tropical Africa on the other. Penchaeta 

 is perhaps a better example still ; the impression gained from the details as to the 

 distribution of this genus given in the present work may not appear at first sight 

 to favour this statement ; the genus is. it is true, found in most parts of the world ; 

 but it has, nevertheless, a somewhat discontinuous distribution ; it is excessively 

 abundant in India and the neighbouring parts of Asia; this is, indeed, the head 

 quarters ; it is rare at the very most in tropical Africa, and reappears, though it is 

 not common, at the Cape. Three species of Perichaeta (s.s.) live in Australia, 

 together with a number of Megascolex; it is very common in several islands of the 

 West Indian group, rarer in South America. The distribution of the family does 

 not suggest a migration from the head quarters, except in the case of the genus 

 Megascolex; it is rather suggestive of a former universal range which has become 

 here and there limited, and here and there perhaps increased in numbers where there has 

 been but little competition. The distribution of worms in Australia offers particularly 

 useful data ; if the general theory to account for the almost entire absence of 

 placental mammals from this region of the globe be accepted, we should argue that 

 the Geoscolicidae, which are totally absent from Australia ^, are a comparatively modern 

 * type, while the Perichaetidae and the Cryptodrilidae, which are so abundant there, 

 are more ancient ; this is quite in agreement wjih the other facts ; for there can be 

 no doubt that the Cryptodrilidae are very nearly akin to the Perichaetidae. 



In considering the distribution of earthworms we are always fairly sure of our 

 deductions, if we can only eliminate the interference of man ; the Perichaetidae 

 and Crj ptodrilidae are too abundant in Australia to allow of our explaining their 

 presence by artificial introduction ; they must obviously be indigenous to that 

 country; the occasional occurrence of a species in a country far from its usual 

 habitat, may, of course, be a fact of importance ; but, considering the possibility of 

 accidental transport, it is not as a rule striking. I should be inclined, therefore, to 

 lay some stress upon the probability of the archaic nature of the characteristic 

 earthworms of Australia,. 



Apart from geographical distribution there appear to me to be other characters 

 which tend to argue for the primitive position of the Perichaetidae among earthworms. 



' Pontoscolex coretJmirus (see p. 150) may be an accidental importation. 



