228 LORANDE LOSS WOODRUFF 
From the study of the monads in all the cultures it is clear that 
in every instance they were the first type of protozoon to appear 
and the first to reach a maximum. This is undoubtedly to be 
explained by the fact that these forms, combining holozoic and 
saprozoic methods of nutrition, are able to feed on the bacteria 
which are developing so rapidly at this period, and also to absorb 
various substances entering into solution from the hay. The 
monads under consideration are also the first forms to decline 
and practically disappear, and this is probably due, in part, to 
the rapid decrease in numbers of the bacteria brought about by the 
monads themselves and by the rising generations of Colpoda. 
2. Colpoda 
A I group. Colpoda was the second protozoon to appear in 
considerable numbers and its maximum was attained on the 14th 
day when there were about 2500 per ec. Its decline was equally 
rapid and by the 25th day very few active individuals were seen. 
Beginning at about the 30th day, however, more were observed 
and on the 37th day there were about 600 per cc. This second 
rise in numbers was followed by a more gradual decline which 
ended in the extinction of this form by the 66th day of the life 
of the infusions. 
A IT group. This form was the second to appear and very 
slowly attained its maximum of 1000 per ce., which took place on 
the 27th day, then it fell in number to about 200 per cc., rose 
again to about 500 per cc. on the 44th day, and then became ex- 
tinct on the 49th day. 
A III group. Colpoda was the second protozoon to appear in 
considerable numbers in these infusions, the cycle of the monads 
being apparently aborted. Colpoda arose abruptly to the great 
number of 15,000 per ce. on the 10th day, fell to about 11,000 per 
ee. on the following day, and by the 15th day very few active 
forms were observed. However, almost immediately it had an- 
other period of reproductive activity which brought up the num- 
ber to about 4000 per cc. on the 29th day. After this second high 
point it decreased in number, but persisted until the 63rd day 
