Juday—Invertebrates Living under Anaerobic Conditions. 13 
Prorodon, Lacrymaria, Uronema and Monas. All of these 
forms were perfectly normal. They did not show any unusual 
vacuolation, nor any other visible evidences whatever of ill 
effects resulting from the anaerobic conditions under which 
they are living. This result does not agree with some of those 
that have been obtained in experiments along this line. Bud- 
gett 4 found that the membrane in many Infusoria bursts and 
the liquid contents flow out when they are subjected to anaeru- 
bic conditions. Putter 5 observed characteristic changes in the 
protoplasm of Paramecium and Spirostomum when they were 
placed in an atmosphere of nitrogen. Loeb and Hardesty 6 also 
observed that amoebae and Paramecium became vacuolated and 
finally burst when deprived of free oxygen. In the experi¬ 
ments, however, the change to anaerobic conditions was made 
rather suddenly, so that the Protozoa did not have time to ad¬ 
just themselves gradually to the new conditions. This sudden 
change to an atmosphere of nitrogen or hydrogen, in which 
the experiments were performed, affected the equilibrium of 
the gases contained in the Protozoa and doubtless resulted in 
a rather rapid diffusion of gases into and out of them wdiich 
may have been largely responsible for the deleterious effects 
that were observed. In the lower water of Lake Mendota, 
however, the change to anaerobic conditions is gradual, thus 
giving the Protozoa time to adjust themselves to the change, 
and they show no visible effect resulting from it. Neither was 
there any noticeable effect when they were changed back again 
to aerobic conditions by exposing them to the air. 
All of the above Protozoa seemed to experience no difficulty 
in withstanding this anaerobic condition for a considerable 
period of time. They were still found as active and in as 
great abundance in late September and early October, after 
the water had been free from dissolved oxygen for nearly three 
months, as in early July at the time of its disappearance. 
Putter 7 also found that he could keep specimens of Nyctoiherus 
4 Budgett, Amer. Jour. Physiol., vol. 1, p. 210. 1898. 
s Putter, Zeitschr. f. allg. Physiol., Bd. 5, pp. 592, 596. 1905. 
e Loeb, “Dynamics of Living Matter,” p. 21. 1906. 
7 Putter, Zeitschr. f. allg. Physiol., Bd. 5, p. 583. 1905. 
