ON THE NEJ[ATODES OP THE COMMON EARTHWORM. 619 
their identity, and therefore I have done this myself. Larvae 
from the nephridia of aLumh. terrestris were put in a 
watch-glass with small strips of decaying body-wall and a 
little water. Glrowth was rapid. When sexnally mature they 
were examined and were found to be Rhabditis pellio. 
The nephridiiil aud coelomic larvae, therefore, are the active 
and encysted forms respectively of one and the same species. 
'I'his has beeu confirmed by all subsequent cultures. Further, 
I have found no other species but this inhabiting the living- 
worm. 
Confusion op Two Species under One Name. 
A perusal of the literature on Rhabditis pellio leads 
one to suppose that all the nematodes Avhich have been 
encountered in connection with the earthworm and described 
under this name ai-e genuine inhabitants of the healthy worm 
and belong to a single species. But whether this is really so, 
and whether the name does not require to be more clearly 
defined, are questions which I propose to discuss. 
I have mentioned earlier in this paper in the survey of the 
literature that Biitschli (6) noticed certain diffei-ences between 
the adult individuals of Rh. pellio which he examined 
and those which had been described by Anton Schneider (1). 
'I'here were various minor discrepancies. But the most 
striking })oiut of dissimilarity was that the tail of Schneider’s 
males did not project beyond the edge of the bursa, while 
that of Biitschli’s males was jn-olonged to a fine point a short 
distance beyond the margin, whicli was slightly notched at 
the place of emergence. 
Biitschli regarded these differences as unimportant, and 
supposed that the two different forms of bursa merged into one 
another by imperceptible gradations. Subsequent references 
to Rh. pellio in the literature of the Nematoda are for 
the most part very meagre. With the exception of Maupas, 
the writers do not comment on the dissimilarity of the two 
forms. Maupas (10), however, twenty-six years after the 
