52 EARTHWORMS AND THEIR ALLIES [CH. 



with their original describers in regarding as definite 

 species. 



It cannot be said that any salient characters in 

 the organisation of these worms mark them out from 

 either terrestrial or fresh-water Oligochaeta. There 

 are no such important variations of structure as can 

 be seized upon to characterise them as inured to 

 salt water. The genus agrees with many aquatic 

 forms in the fact that the nephridia are not present 

 in the earlier segments of the body, not indeed putting 

 in an appearance until about the thirteenth segment 

 or even later. They are thin delicate worms; but 

 there is nothing distinguishing about this, while the 

 feeble or absent gizzard is a character which is really 

 difficult to correlate with habitat. Still we have here 

 a whole genus which is marine in its habit. Among 

 the Megadrili oi earthworms there are not many 

 other examples of these 'euryhaline ' forms as they 

 have been named. On the shores of Patagonia how- 

 ever and Kerguelen shore-living species of the mainly 

 antarctic genus of earthworms Notiodrilus have been 

 met with. And there are a few allied cases among 

 the antarctic genera of Acanthodrilinae. 



In addition to these terrestrial forms there are 

 a few limicoline genera which are partly marine in 

 their habit. Thus several species of the prevalently 

 arctic and antarctic family Enchytraeidae are shore 

 living. There are also marine Tubificids such as 



