284 ANTARCTICA. 



About fifteen years ago Beddard obtained from a subter- 

 ranean well in New Zealand a new aquatic genus which he 

 described under the name Phreodrilus. This form was so pecu- 

 liar that it could not be included in any of the known families of 

 this group of worms. It was then found that forms which had 

 been found in South America and the Falkland Islands, and had 

 been described under another name, belonged to the same genus. 

 Since then a special family has been created to include these 

 forms and others which have now been found in Falkland 

 Islands, New Zealand, Campbell Islands, Australia, Tasmania, 

 Kerguelen Island, and South Africa. 



Anatomical evidence supports the idea that the family is an 

 ancient assemblage, and their habitat taken into consideration in 

 conjunction with their circumpolar distribution is interesting. 

 With the exception of one genus, which is unique among the 

 group in that it lives in close semiparasitic association with the 

 freshwater crayfish — Astacopsis — of Australia, they are re- 

 stricted to cold habitats. These conditions are obtained in some 

 cases through the latitude of the habitat, in others by extreme 

 bathymetrical isolation assisted by the seasons. In South Africa, 

 for example, they have been collected on Wellington Mountains, 

 Stellenbosch Mountain, and Table Mountain, but further, not 

 only does investigation show that they are inhabitants of moun- 

 tains solely, but also that they disappear in some manner or other 

 — no doubt into the soil — during the hot months of the year. 



In noting their restriction to cold habitats and to the 

 Southern Hemisphere it must be borne in mind that no repre- 

 sentatives have been found in the Northern Hemisphere, which 

 has been much more seriously investigated in the past. This is 

 very significant. The fact that they are restricted to habitats 

 with low temperatures may be rationally interpreted as signifying 

 that such a common feature is characteristic of the group, and 

 in all probability of their common ancestral stock, or as the result 

 of their inability of carrying on the struggle for existence in 

 habitats where other forms of Oligochccta, etc., find favourable 

 conditions. 



The question now arises, whether the Phreodrilidae enjoyed 

 at one time a much wider distribution and have since disappeared 

 in most parts, or whether we are to regard them as forms which 

 made their appearance in the Southern Hemisphere. 



Now, it is interesting here to note that although none of the 

 group is known in the Northern Hemisphere, yet in that region 

 there occurs a family — Lumbriculidae — which is unknown in the 

 Southern Hemisphere. Further, this latter family occupies a 

 position of the same phylogenetic status as do the Phreodrilidae 

 between the two main divisions of the Oligochaete worms, and 

 this is significant when their respective restricted distributions 

 are considered. Both may have arisen, and no doubt did, from 

 a common stock, and it seems highly probable that they have been 

 evolved in the regions now occupied by them. That there has 

 been no intermingling of the two races and no spreading into 



