III. 

 Earthworms and the Earth's History. 



THERE has been recently a considerable discussion in the pages 

 of Nature as to the probability of a former extension northwards 

 of the antarctic continent. The discussion has also affected the 

 columns of this Journal, which published last month an abstract of 

 the recent views of Mr. H. O. Forbes on the subject. Mr. Forbes 

 believes in this continent. We quite agree with him, though for 

 reasons different to those which he urges. 



It seems to be an obvious platitude that those animals are most 

 important for use in arguments relating to the past connection of land 

 masses which do not migrate of their own free will across the sea, 

 and are incapable of being carried over by accidental modes of transit, 

 and yet, with one exception to be mentioned presently, the group of 

 all others which best fulfils these conditions has been completely 

 ignored by writers on the subject of geographical distribution. The 

 group to which we refer is that of the earthworms. 



The earthworm, like the agricultural labourer, is wedded to the 

 soil ; more so, indeed, for the labourer does occasionally emigrate, 

 but the earthworm never, and for the very good reason that sea-water 

 is fatal to his constitution. Although earthworms do not apparently 

 ever cross the sea by any of those modes of transit which are held to 

 account for the range of other animals, there is sometimes (again like 

 the agricultural labourer) " assisted emigration." Commerce between 

 different countries is apparently responsible for the transference of 

 earthworms from one country to another — particularly, of course, 

 the exportation and importation of plants. That this is really the 

 case is capable of the easiest proof; any collection of living plants 

 from a foreign country is nearly sure to contain a few worms, besides, 

 of course, insects and other small creatures. Indirect but still con- 

 vincing proof of man's agency in affecting the distribution of earth- 

 worms is shown by the wide range of the common earthworms of 

 Europe which belong to the genera Lumbricns and Allolobophora. In 

 Europe and North America these two genera are the prevailing types, 

 to the neafly complete exclusion of any others. In such distant and 

 widely-separated regions as New Zealand and South America, the 

 same genera are met with, but they are not the prevailing types. 



Now, there is not, so far as I am aware, a single exception to 



