THE BOTTLE ANIMALCULE, FOLLICULIXA. 267 



though in aquaria they lived till the 27th and in a warm room 

 till November II, though in a faded and apparently starving 

 state. In 1913 there was a sudden disappearance of most all 

 live Folliculina, leaving chiefly empty tubes, after a sudden 

 drop of temperature from 97 F. to 60 F. with rain. No live 

 ones could be found after September 5 after cold rain, though 

 found September I in a very few examples after much search. 



By September 22 with the water at 83 F. and air at 80 F. 

 no tubes even could be found except in places where the plant 

 had not recently grown enough to shed the leaves to which the 

 Folliculina tubes had been long attached. 



Such empty tubes remaining upon old leaves that have not yet 

 fallen off, illustrates one phase of the correlation between Folli- 

 culina and the growth of the plants. 



Followed from spring onw r ard the distribution of the living 

 Folliculina is nicely adjusted to the growth of the plants, as will 

 be seen from the following. 



May 17, 1913, no Folliculina had yet appeared, but the Elodea 

 zone denuded all winter had begun to be repopulated with new 

 plants shooting up three inches high, apparently from old bits 

 of stem buried in the mud. These plants were then perfectly 

 clean and bright with no inhabitants save a few minute young 

 snails. Some of the cells of the Elodea, however, were already 

 dead here and there, apparently from some parasite; but this 

 was not connected with Folliculina that at present was in some 

 unknown state. The Potamogeton zone showed stalks eighteen 

 inches high \vith some few flower buds far from the surface of the 

 water. 



By June first the Potamogeton had flowers near the surface 

 and the Elodea was 12 to 15 inches high and no longer entirely 

 clean but with the older lower leaves covered with a flocculent 

 deposit and supporting many colonial vorticellids seen to the eye 

 as contractile tufts on single stalks. Two weeks later, the 

 Elodea was two feet high with flowers on stems four to six inches 

 above leaves and some open flowers at surface. The Pota- 

 mogeton now was three feet high with flowers at the surface of 

 water. But all the leaves were covered with dirt and no Follicul- 

 lina was found. On the 27th, Folliculina was found as black 



