1^02 



stated before, the sprinkling filter is a device for oxygenating the 

 sewage which is delivered to it, thus rendering it more stable, hence 

 the presence of anything in the filter which draws upon the oxygen is 

 thus decreasing the efficiency of the filter. The evidence seems to be 

 conclusive that the presence of these worms in the sprinkling filter 

 increases the putrescibility of the sewage by using up a part of the 

 available oxygen, and since they occur in great numbers in the sprin- 

 kling filters for the greater part of the year there is good reason to 

 believe that in so far as their relation to the available oxygen is con- 

 cerned the effect O'f their presence in the sprinkling filter is a detri- 

 mental one. If, on the other hand, it be true that at all times of the 

 year there is a distinct vertical distribution of the worms in the 

 sprinkling-filter, in which the larger number is confined to the upper 

 two or three feet, the detrimental effects of their presence may be 

 overcome to some extent, since the interstices of the filter stones con- 

 stitute air spaces by means of which the loss of oxygen in the upper 

 zone due to the activity of the worms may be mitigated to some ex- 

 tent by the passage of the sewage through the air spaces of the lower 

 parts of the filter bed. Nevertheless, the fact remains that the worms 

 increase putrescibility, and their presence in sprinkling- filters is ap- 

 parently undesirable. It is possible that when the problem of the re- 

 lation of these worms to sewage has been completely worked out it 

 may be found that the advantageous relations may more than offset 

 the harmful ones, but until further investigation is made this point 

 must remain unsettled. 



Summary 



1. The following new species of Bnchytrccidcr, distributed among 

 four genera, have been added to the list of American forms. 



Name Type locality 



Henlea modcrata Urbana, 111. 



Henlea itrbanensis Urbana, 111. 



Lumbricillus rntihis Chicago, 111. 



Fridericia donglascnsis Douglas Lake, Mich. 



Fridcricia oconeensis Oconee, 111. 



Fridericia sima Urbana, 111. 



Bnchytrcrns gillettcnsis Gillette Grove, Iowa 



2. Chylus cells were found only in Fridericia. The characters 

 of these cells are distinct for each species examined, and show evi- 

 dence of taxonomic value. 



