DEGENERATION OF INTERNAL ORGANS 237 



Tierra del Fuego, the Falkland Islands, South Georgia, Kerguelen, the Crozets, and the 

 southern islands of the New Zealand region. 



E. australis in South Georgia and Gough Island (in mid- Atlantic, not far from Tristan 

 d'Acunha). 



All the above genera of Enchytraeidae are known from Europe, and Marionina, 

 Lumbricilliis, and Etichytraeus, which are among the commonest representatives of the 

 family, from North America also. 



Though Rhyacodrilus coccineiis (Tubificidae), recorded from South Georgia by 

 Michaelsen (1905), was not obtained by the present expedition, it is interesting to note 

 that it occurs in Europe, in the Crozets (Michaelsen, 1905 a), and in New Zealand 

 (= Taupodriliis simplex, Benham, 1903). 



Though the above presentation contains some rather striking facts, such as the occur- 

 rence of LiimbriciUus macquariensis only in the widely separated localities of South 

 Georgia and the southern islands of the New Zealand region, and similarly of Efichytraeus 

 australis only in South Georgia and Gough Island, it can, owing to the ease with which 

 these worms or their cocoons can be transported, hardly be said to contribute data of 

 much value for zoogeographical discussion. We cannot rule out transport by human 

 agency or by natural forces; though, of course, while the facts give no support to the 

 view of a recent temperate Antarctica as a factor in zoological distribution, they are at 

 least not against it. 



DEGENERATION OF THE INTERNAL ORGANS IN THE 



ENCHYTRAEIDAE 



In a number of the worms in the present collection the task of identification and 

 description was rendered difficult or even (as in the specimen belonging to the genus 

 Achaeta) impossible by a marked degeneration of the interior of the animal. 



This condition was very common in the numerous specimens of LiimbriciUus maximiis, 

 the most abundantly represented species in the collection ; in most of the batches some, 

 it might be even all, of the worms showed the change. In the body wall the muscular 

 layers were breaking up, the longitudinal muscle coat was losing its continuity and its 

 cohesion, small lengths of muscle fibres were being shed and a number of such frag- 

 ments were loose in the anterior segments, where they were apparently becoming 

 converted into a homogeneous somewhat waxy-looking substance. Some of the lymph 

 corpuscles were vacuolated, and many were disintegrating. 



The alimentary canal shows the degenerative changes in a very marked degree. The 

 pharynx breaks up with the formation of vacuolar spaces, and the setting free of small 

 round or irregular cells and non-nucleated fragments. The cells of the alimentary 

 epithelium are shed into the cavity ; in the preclitellar segments the oesophagus is seen 

 to have lost the whole of its epithelial lining, and its lumen is full of small irregular cells 

 and granular debris; behind segment 14 there is a regular epithelial layer, which here 

 and there is becoming detached but is still continuous. 



