306 GRIFFIN. 



counter clock-wise, for numerous small revolutions about the central 

 region of the body. The e.yelosis is continual but irregular in rate, and 

 much more restricted in extent than in most large ciliates. The endosare 

 of the edges and anterior and posterior extremities of the body seems to 

 be very stable. 



The place of egestion is immediately behind the outermost anal cirrus, 

 on the ventral surface. Frequently large quantities of indigestible 

 material accumulate in the body before egestion takes place. Then the 

 balls of ejecta are pushed out with considerable force, at intervals of a few 

 seconds, until all is disposed of. The slowness with which the masses 

 of ejecta are at first pushed through the surface of the body, until the 

 largest part passes the pellicle, and the suddenness and force with which 

 they then are shot away, indicate that the pellicle around the anus is 

 highly elastic and that the anus is kept closed by its contraction. It 

 appears probable that in those ciliata which possess a definite anal spot, 

 there is also a real canal in the protoplasm, ordinarily kept closed and 

 invisible by the elasticity of its walls and the pellicle. 



As the anus lies just in front of the contractile vacuole, the masses of 

 ejecta often press against its walls. In some cases the masses of un- 

 digested material accuniidate to such an extent as actuallj' to be forced 

 into the contractile vacuole and cause it to become enonnously distended ; 

 but in most cases this organ is only crowded to one side and partially 

 surrounds the mass of waste material, the appearance that ejecta are 

 inside the vacuole being deceptive. 



Conimctile vacuole. — The position of this organ is shown by Plate I, 

 figure 1. When fully formed the vacuole is rather large. The pulsations 

 occur at unusually long intervals. Because of the slowness of the process 

 it is difficult to watch the entire cycle in an animal active enough to make 

 the observer sure that it is in a normal condition. ■ I find that the time 

 required for the complete cycle averages twelve miniites. If, as has been 

 suggested, a principal function of the vacuole is to force out of the Ijody 

 water which is continually being taken in with the food particles, the 

 long j)eriod of the vacuole of Euplotes may very well be due to the 

 extremely minute quantities of water absorljed with the food. The length 

 of time required for a cycle of the contractile vacuole in this species is 

 the more remarkable since Eossbach gives 31 seconds as the period of 

 Euplotes cliaron 0. F. M., and Maupas 50 seconds as that of E. patella 

 0. F. M. I find no statement concerning ■ the contractile vacuole of 

 E. vannus 0. F. M. in the siimmary of Minkiewicz's paper. It is possible . 

 that in this genus we have an opportunity to test the theory of a relation 

 Ijetween the amount of water swallowed with the food and the activity of 

 the contractile vacuole. Another indication of the low activity of the 

 contractile vacuole of this species is in the fact that at any time large 

 numbers of healthy animals show no vacuole at all. Out of twenty which 

 were carefully examined at one time, the examination of each reqiiiring 



