20 University of California PuMi cat ions in Zoology [Vol. 18 



impulses, this unified system has been compared to the nervous sys- 

 tem of metazoans, and is probably more closely allied to the mechanism 

 of the reflex arc, and therefore called the neuromotor apparatus. The 

 fibrils stain red in Mallory's connective-tissue stain, which is char- 

 acteristic of nervous fibrils in the Metazoa. 



The neuromotor apparatus forms one entire integrated system for 

 regulating and controlling the motor activities of the organism. The 

 fibrillar division of this apparatus, composed of the eight flagella and 

 their intracytoplasmic portions, are the organelles for locomotion. In 

 the study of living forms all flagella are seen to vibrate synchronously 

 and with the same rapidity when the flagellate lies upon its dorsum. 

 The members of each pair of flagella vibrate together and at the same 

 rate. The axostyle also undulates, as do the intracytoplasmic portions 

 of the posterolateral flagella, the waves of vibration commencing at 

 their proximal ends and continuing outward to the ends of the free 

 flagella. When an increased rate of locomotion takes place it results 

 from increased activity of all the flagella. It appears that the course 

 of the animal in locomotion is directed by the tail, Avhich acts as a 

 rudder bending up and down, or from side to side. When the flagel- 

 late comes in contact with an obstacle the axostyle, because of its 

 rigidity, serves as a lever to push away from the impediment. 



The turning or rotating movement of the flagellate in locomotion 

 is due to the combination of three factors — the concavity present 

 between the intracytoplasmic portions of the posterolateral flagella; 

 the action of the axostyle in bending up and down and from side to 

 side ; and the position and increased activity of the flagella ; the direc- 

 tion of their stroke, whether straight back or oblique, is dependent 

 on the position of the flagella, an oblique direction of the stroke tend- 

 ing to rotate the organism (pi. 1, fig. 8). 



Cysts 

 The cysts of G. microti are ellipsoidal in shape, varying in size 

 from 6.7x8.5/A to 7x13. 3/^. In all cases these cysts are easily identified 

 by the thick, firm cyst-wall and the scattered remains, now and then 

 still intact, of the parabasal bodies and of the neuromotor apparatus. 

 The cysts occur both in the small and large intestine, but predomi- 

 nantly in the latter. Many of the cysts show a condensation of the 

 protoplasm and its withdrawal from the cyst-wall (pi. 1, figs. 13, 16). 

 This is probably due to plasmolysis at the time of fixation in the prepa- 

 ration of the material. 



