204 



that a maximum of contact with the sludge and the filter-bed rock is 

 secured. 



The maximum life-limit temperature for these organisms is very 

 near 36 degrees Centigrade. In temperatures ranging from 25 to 10 

 degrees no difiference in the activities of the worms was noticed, but 

 from 10 to 2 degrees activity was reduced. They can live in a tem- 

 perature of 5 degrees for days and even weeks. 



These worms require an abundant supply of oxygen. Continued 

 low dissolved-oxygen content in the medium has a deleterious ef- 

 fect, and the great abundance of these forms in the sprinkling filters 

 is due in part to the high dissolved-oxygen content of the sewage 

 which comes in contact with them. They can not thrive in crude 

 sewage. 



The worms show a distinct recognition of the presence of sludge, 

 and react positively to it. In the sprinkling filters they loosen up 

 the accumulating sludge and work it over, thus facilitating the oxida- 

 tion of the unstable organic matter. Circumstantial evidence indi- 

 cates that it is at least partly through the agency of these worms that 

 the "unloading'' of the sprinkling filter occurs in spring. 



Experiments have shown that these worms increase the putresci- 

 bility of the sewage in which they occur. This is a fact of economic 

 importance. They thus interfere with the efficiency of the sprinkling 

 filter and aid in rendering the sewage unstable, faciliating anaerobic 

 decomposition. In this particular respect they are undesirable organ- 

 isms in sewage disposal plants. 



