62 EARTHWORMS AND THEIR ALLIES [ch. 



with the migration of these animals. On the other 

 hand the Lumbricidae have on the whole a more 

 extensive clitellum and so have many Geoscolecidae. 

 It is obvious that of all earthworms the Lumbricidae 

 is the family which has the greatest capacity of 

 migration and adaptation to new circumstances. 

 The reason for this may be that in the latter case 

 the more extensive clitellum produces a larger cocoon 

 which in its turn can hold and cherish while they 

 reach maturity a larger number of embryos. Much 

 remains to be learnt under this heading. But the 

 comparatively small clitellum of the large Ceylon 

 Megascolex coeruleus only contains two embryos, 

 while the also comparatively small cocoon of the 

 large and restricted Octochaetus multiporus (limited 

 to the South Island of New Zealand) only contains 

 a single embryo. This latter fact may be regarded 

 as fairly well established since I myself examined 

 quite fifty cocoons. 



On the other hand larger numbers seem to arrive 

 at maturity in the cocoons of Allolohophora. The 

 more extensive clitellum must produce a relatively 

 larger cocoon, and it is interesting to note that the 

 cocoon of the widely distributed genus Criodrilus 

 (Europe and South America) is very long although 

 not of great diameter. However the facts are not 

 sufficiently great to dogmatise much upon this 

 subject. Another conceivable reason for differences 



