622 
GILBEET E. JOHNSON. 
cribed was a distinct species from that of Schneider was 
evidently because Schneider’s form, like bis own, had occurred 
on decaying worms, and he did not realise that the presence 
of soil allows chances of contamination with soil-inhabit- 
ing forms. 
It may be asked why neither writer recorded the form 
described by the other. The explanation may be that 
Biitschli probably did not find his infected earthworms de- 
caying in soil like Schneider’s, but killed them himself and 
allowed them to decay in water, in which case the “ pelo- 
derian ” form would not be present; and that Schneider 
made his description from only a few individuals, amongst 
which none of the “ leptoderian ” species happened to be 
included. 
With the notable exception of Maupas, later writers, as I 
said before, do not comment on the difference of the two 
forms. The probable reason was that they saw Biitschli’s 
“ leptoderian ” form only, because soil was excluded from 
contact with the putrefying- worms which they used, or they 
may have seen both forms but did not suspect them to be 
distinct species because they did not recognise that the soil 
is a source of contamination.^ 
In view, then, of the confusion, under the same name, of 
two undoubtedly distinct species found in the same situation 
in the adult state but derived probably from different 'larval 
habitats, I propose to distinguish between them by narrowing 
the application of the name. I propose to restrict the name 
Rhabditis pellio Schneider to the “ peloderian ” form 
described by Schneider, and provisionally to designate the 
' Since writing the above I have been able to consult Orley's ‘ Die 
Rbabditiden nnd ibre mediciniscbe Bedentnng,’ Berlin, 1886 (14). The 
tail of the male Rh. i^ellio which he describes (p. 33) is of the “pelo- 
derian ” type and closely resembles that of Schneider's form. But 
whether he made his description from adults l)red, without risk of con- 
tamination with soil nematodes, from larvEB actually inhabiting the 
living worm, and not from adults obtained from dead woi-ms allowed 
to decay on soil (his method of obtaining large numbers of nematodes) 
appears to be doubtful. 
