GEOTROPISM OF THE MARINE SNAIL, LITTORINA LITTOREA. 79 



up or down." It is fair to examine the table (V.) which is given 

 by Frandsen based on his results. Take the animal No. "13," 

 on which the series of observations, "a" and "" were made. 

 The condition of the animal was "active" in series "a" and also 

 in series "6," that is, it was under the "same" condition. 

 Being the same individual, theoretically there was no difference 

 in the "ratio." Nevertheless, Frandsen obtained different 

 results in "a" from "6." Moreover, he shows different results 

 in the same individual under the same condition and in the same 

 series of observations, "a" or "6." This is more striking in 

 the animal No. "23," on which the series of observations, "a," 

 "&," "c" and "d," were made under the same condition, "good." 

 But he obtained 64.2 per cent, of negative geotropism in series 

 "a," 62.5 per cent, in the "b," 100 per cent, in the "c," and 100 

 per cent, in the "d." In other words, the same individual under 

 the same condition was, at least, 35.7 per cent, positive in "a," 

 37.4 per cent, in "&," and o percent, in "c" and "d." This kind 

 of variation is also found in the animals Nos. "8," "24," "25" 

 and "27." If so, "all the conditions being the same," it is not 

 entirely the first factor, nor the second, "which 'determines 

 whether the head end will be directed up or down,' ' but there 

 must be something else besides these two factors, which makes 

 the response variable. Frandsen does not seem, therefore, to be 

 justified even by his experimental data in his conclusions. And 

 strictly speaking, the so-called mechanical theory of geotropism 

 seems to the writer to be misleading in any case, because it is 

 not a living response to stimulus but a purely mechanical one 

 which would be seen as well in the dead organism, if it could be 

 moved. This is no tropism at all. 



In this respect, therefore, the writer is inclined to take Daven- 

 port and Perkins's conclusion into consideration, as, at least, one 

 of the factors, that is, "some internal condition of the individual." 

 Without this "internal," or physiological, factor, it is difficult to 

 explain why geotropism varies in the different individuals and also 

 in the same individual at the different angles of inclination of the 

 same support and the same angle of inclination of different 

 supports. 



Haseman's conclusions demand close consideration on several 



