2JO E. A. ANDREWS. 



is a constant succession of new tubes formed above on the more 

 recent leaves while lower down the old tubes are doomed to be 

 dropped off from the macreated leaves to the bottom where they 

 long resist decay. Both the gradual spread of FoUiculina tubes 

 from the first seen on the tips of the leaves over the entire expanse 

 of upper leaves and the secondary migration from these leaves 

 ever upward to other leaves as they grow out from the terminal 

 buds might be accounted for on the hypothesis that the entire 

 occurrence of FoUiculina in these waters is the result of inocu- 

 lation each spring with new individuals from outside the region 

 and the rapid multiplication, spread and autumnal destruction, 

 under seasonal changes of environment. 



SESSILE AND MOTILE FORMS. 



Direct observations in aquaria showed that many of the above 

 facts as to the attachment and occurrence of tubes were due to 

 the existence and behavior of free swimming motile states of this 

 animal. When brought into dishes of various kinds these 

 motile forms soon swarm out from the tubes and construct tubes 

 attached to the sides of the dish. Under the microscope, some 

 of the FoUiculina were seen to emerge from the tubes and to 

 eventually swim free in the water. With the naked eye the free 

 swimmers were followed in the aquarium till they became at- 

 tached to its sides. When the Elodea was collected in the evening 

 free swimmers were found the next morning and made new tubes 

 during the day. In this way as many as four successive crops 

 of newly attaching FoUiculina were obtained in successive days 

 from one collection of Elodea. The newly settled animals lived 

 probably at least two weeks though the longest observation of 

 individuals was nine days. 



While most of the new swimmers came from old tubes on the 

 Elodea there was good evidence that the new tubes formed in 

 captivity gave rise to swimming forms. When collected early 

 in the morning free forms were found before noon and new sessile 

 forms were made in the afternoon. While the temperature 

 seemed to influence the times, in general no swimmers were 

 liberated in the night but began about seven or eight in the 

 morning and swam two to several hours; about noon the sessile 



