338 Hoyt: CULTURES OF SPIROGYRA 
water drawn from the tap at the same time, nearly all the fila- 
ments succumbed within a few hours (II, 8). Heating tap water 
to a temperature of 100° C. in a steam sterilizer for 45 minutes 
produced no improvement; the filaments of Spirogyra died almost 
as quickly in this as in untreated water (II, 9). 
Treatment of the tap water of the Heidelberg supply by the 
method of shaking with finely divided carbon, as employed with 
such marked effect by Livingston in the preparation of culture 
media from his ordinary distilled water, produced no improve- 
ment. In this treatment Merck’s ‘‘animal charcoal’? was em- 
ployed as absorbing solid, without preliminary treatment of any 
sort. While it seems probable that there may be essential differ- 
ences between the various forms of finely divided carbon now upon 
the market, as to their efficiency in the water treatments here con- 
sidered, no comparisons have been made in this regard. The form 
here used was chosen merely because of its convenience. 
Although, as has been pointed out, simple distillation of the 
Heidelberg tap water from glass into glass failed to correct the 
toxicity of the water, it was found that this same process of dis- 
tillation rendered the water nontoxic to the Spirogyra here em- 
ployed (II, 10) when animal charcoal was present in the retort during 
the distillation. In this treatment the boiler was a flask of Jena 
glass having a capacity of one liter; the condenser was of glass, 
provided with a bend to prevent the entrance of spray from the 
boiling liquid and thoroughly washed by use; and the receiver 
was a flask of Jena glass. Nocork or rubber or material other than 
glass was used on the condenser. The usual charge was about 800 
cc. of tap water with from five to ten grams of Merck’s animal 
charcoal. Boiling was not allowed to become very violent and the 
‘process was stopped when the charge had been reduced to about 
one eighth of its original volume. In water thus prepared Spiro- 
gyra filaments remained in apparently healthy condition until the 
appearance of injury from lack of nutrient salts. 
This method of distillation from animal charcoal showed some 
variation in the quality of the water produced (II, 10), but the 
differences exhibited were not as great as those obtained with 
different portions of water from the stock culture (III, 36). The 
water distilled from charcoal was frequently tested throughout 
