THE GEOTROPISM OF PARAMECIUM CAUDATUM. ilj 



that mechanical agitation of transferring may be responsible for 

 it. Sosnowski also suggested this factor in one case, "die Tem- 

 peraturerhohung und Erschiitterung sich zu summieren scheinen" 

 The reversibility of the negative geotropism of the animals by 

 mechanical "shock" or agitation is a well-known fact. The 

 water current may also help it to some extent. 



From these results the writer concludes that so-called rever- 

 sibility of the negative geotropism of Paramecium by tempera- 

 ture is extremely doubtful.. Especially in such cold water as 

 near i C., the animal is almost, if not thoroughly anesthetized. 

 In consequence, it sinks by its weight, though Moore thinks it is 

 "reversed." 



4. Do chemicals reverse the negative geotropism of Para- 

 mecium caudatum? 



According to Sosnowski, "durch Zusatz geringerer Mengen 

 von Sauren oder Alkalien (i bis 3 c.c. Salzsaure oder Natron - 

 lauge von 0.5 per cent, auf 20 c.c. Culturfliissigkeit) kann man 

 verubergehenden positiven Geotropismus hervorufen." Moore 

 also states that "in n/i6 NaCl, they went to the bottom almost 

 immediately, but shortly after died." In a solution of calcium 

 chloride isosmotic with 11/32, "they went immediately to the 

 bottom." 



The writer attempted to test these statements of Sosnowski 

 and Moore. First of all, he thoroughly washed the animals in 

 boiled then cooled tap water. Chemical solutions from the 

 strongest to the weakest were carefully prepared using boiled 

 tap water. A few drops of culture containing dense Paramecia 

 were transferred with special care to avoid making water currents 

 as much as possible. The results given in Table II. are to be 

 considered as the best parts of many series of experiments that 

 were quite extensively carried out. 



As the table shows, the majority of the animals always swam 

 downward, i. e., were positively geotropic, whenever transferred 

 into any solution as well as in the control, i. e., transfer into 

 culture water. Among the substances used, perhaps, CaCl 2 

 solution "affected" the animals most. In this respect, Moore's 

 observation seems to be confirmed, but it needs further considera- 

 tion. In any solution, the animals that swam to the bottom did 



