1910 - 11 .] Mathematical Theory of Random Migration. 
283 
Other Crustacea. 
Some copepods were experimented with, but their transparency and 
rate of motion unfitted them for this purpose ; they were also too strongly 
attracted to light. In addition an attempt was made with a fresh-water 
isopod, but a sufficiently large dish could not be obtained to make the 
experiment of any value. 
Littorina rudis. 
Several experiments were made with this mollusc. Numbers were 
placed in various vessels and their movements observed. It was found 
best to put them at the bottom of a deep glass jar with a little salt water 
Distance in 
inches. 
Numbers 
actual. 
Numbers 
theoretical. 
0- -5 
25 
23-2 
•5- 1 
15 
163 
1-1-5 
13 
11-5 
1-5 -2-0 
6 
8-2 
2-0 -2-5 
2 
5-8 
2-5 -3-0 
5 
4-1 
3-0 -3-5 
5 
3 0 
3-5 -4-0 
1 
2-2 
4-0 -4-5 
1 
1-4 
4-5 -5-0 
3 
1-0 
5-0 -5-5 
1 
■7 
5-5-60 
1 
•5 
