THE BOTTLE ANIMALCULE, FOLLICULINA. 283 



away from one another, at 1.08 a fifth animal approached but 

 soon left the group; at 1.09, three were markedly flattened as 

 indicated by the apparent increase in size, while at i.io, they 

 had altered positions and shapes. Such oscillations as shown in 

 these five minutes might ultimately result in adjustments of 

 many as in Fig. 6. The common factor that restricts the motions 

 to small areas may well be the secreted film that limits motions 

 by its adhesiveness. The secretion of the first that put out 

 material in the substratum might delay the swimming of another 

 that came near by, lessening the effectiveness of its cilia, mechan- 

 ically; but other more complex reactions of the second to the 

 secretions of the first may be imagined. 



While the secretions made by those settling down on foreign 

 bodies may somehow determine that other FoUiculina crowd to 

 the same region, special observations and experiments are needed 

 to determine why the cases have the radial arrangement shown 

 in Figs. 3, 4, 6. It is noteworthy that the cases lie either side by 

 side as 1,2, 3, Fig. 6, or else are so placed that their long axes 

 radiate roughly from some central region. In the prevailing 

 radial arrangements the anterior ends of individuals do not face 

 one another but face away from one another at opposite poles of 

 the radii of the group. The behavior of the motile forms indi- 

 cated in Fig. 7, suggests a long series of trials or changes of 

 position leading up to the final position assumed when the cases 

 are made, but these animals did not make their cases for several 

 hours and that seems so abnormal that one cannot rely on these 

 specimens as showing the usual mode of settling down though we 

 make use of them as evidence that they are held in one region by 

 something which may well be the secretions. 



Possibly careful study would show that the currents set up 

 by the cilia would tend to passively drive the animals into the 

 radial position when the posterior end of each is held somewhat 

 passive by the abundant secretion at that end; but on the other 

 hand some of the groupings, and especially the arrangements of 

 Folliculinas that settle down on top of a group that has already 

 made cases suggest that each animal is capable of responding 

 to the presence of others in some complex way, so as to avoid 

 facing another, and so as to fit itself into vacancies amidst a 

 group or to lie parallel to others. 



