189 



Vigorous worms just removed from their natural habitat were used 

 in all of the temperature tests, and tap water was used as the medium. 

 Beginning with water at 2 degrees C., tests were made at every de- 

 gree (in some cases every half degree) up to 45 degrees. Sometimes 

 the process was reversed, the start being at 45 degrees and the tem- 

 perature being reduced by steps of i degree down to 2 degrees C. 

 Unfortunately, facilities were not at hand for making tests with tem- 

 peratures lower than 2 degrees C, and consequently the minimum life 

 temperature was not detennined. All specimens survived 2 degrees 

 C. and were apparently uninjured by it. Results indicated that the 

 maximum temperature is very near 36 degrees C, for while specimens 

 sometimes survived a 36 degrees test an additional half degree proved 

 fatal in a short time, and all temperatures above 38 degrees caused 

 immediate death. The specimens submitted to the higher tempera- 

 tures were observed under the microscope so that the effect of the heat 

 might be judged as accurately as possible. It is interesting to note 

 that these worms seem adapted to withstand successfully rather low 

 temperatures. A series of tests was carried on by putting a consid- 

 erable number of worms into flasks containing water to a depth of 

 about 3 cm. and keeping them in the ice box where the temperature 

 was a trifle less than 5 degrees C. The worms lived indefinitely un- 

 der these conditions. One flask remained in the refrigerator for ten 

 da}-s, and at the end of that time all of the worms were alive, active, 

 and apparently in as good condition as when they were first put in. 

 As to the effect on the activities of the worms, little if any differ- 

 ence could be detected from 10 degrees to 25 degrees C, but below 

 10 degrees activity decreased, only a very moderate manifestation 

 being evident at 2 degrees. It was noted that this decrease in activity 

 was not uniform, being more marked from 5 to 2 degrees than from 

 10 to 5 degrees. Above 25 degrees activity increased as the tempera- 

 ture was raised. 



From these data it would appear that so far as temperature is 

 concerned the worms could exist in the sprinkling filters the year 

 round, since the latter are in constant operation and never freeze. 

 Evidently some factor other than temperature is effective in the re- 

 duction of the numbers of the worms in late summer and autumn. 



RElvATlON TO OXYGEN 



The Normal Supply of Oxygen. — As has been stated before, a 

 sprinkling filter is a device designed primarily to effect the oxidation 

 of the sewage which is delivered to it, and, as a consequence, the 

 organisms which live in these filters are well supplied with oxygen. 



