1919] Rhodes: Binary Fission in Collodictyon triciliatum Carter 217 



when Collodictyon is in a moribund state, giving rise to what France 

 calls water vaeuoles. 2. Water vacuoles : I can not differentiate these 

 from the old food vacuoles except that they are larger. They give 

 similar reaction with Congo red. Undoubtedly they are pathological, in 

 the sense that they do not appear except in moribund condition. The 

 smaller food vacuoles either are entirely absorbed or their contents 

 are extruded. 3. In the moribund state the simple protoplasmic 

 vacuoles may rupture and flow together, thus creating large degenera- 

 tion vacuoles, indicative of a quick collapse. 



"Contractile vesicles" were seen and described by Carter (1865). 

 He did not figure them, however, and merely indicated that their 

 position was so variable that he evidently failed to locate them for his 

 sketches. Stein (1878-83) described one pulsating vacuole in the 

 anterior end and figured the same. Klebs (1893) indicated one in the 

 posterior end of his organism, which neither France nor I believe to be 

 a true Collodictyon. France (1899) found one at the anterior end, 

 about 6/tx in diameter, which pulsated two to three times a minute. He 

 says that it is near the nucleus, but very hard to see on account of 

 the numerous granulations. In all my observations, even with the 

 compound binocular microscope, I have failed to find this vacuole or 

 any other pulsating vacuole. The individuals were often free from 

 inclusions, were studied when actively moving about, when stained 

 intra-vitam with neutral red, Bismarck brown, and methylen blue, when 

 retarded by nicotine, Congo red, anilin solution, litmus solution, weak 

 hydrochloric acid and carbon dioxide. Several times in watching these 

 forms until cytolysis occurred, I have seen the protoplasmic vacuoles 

 flow together, resembling somewhat contractile vacuoles discharging. 

 I am sure these were not pulsating vacuoles. However much I regret 

 to differ from previous observers, especially France, who measured 

 and observed the period of pulsation, I am constrained to believe that 

 in the Collodictyon of the culture under discussion there is no con- 

 tractile vacuole. 



France (1899) sums up most satisfactorily his reasons for believing 

 that there is no cuticle; I agree with him. At the same time, the 

 characteristic form is such, and so constant for the individual, especi- 

 ally for the anterior end, that I am convinced there is a periplast or 

 pellicle, thin and undifferentiated, of smaller vacuoles or homogeneous 

 protoplasm. This must be a coagulation product. It at least is rather 

 impermeable to quick action of many chemicals, especially anilin dyes. 



There is no central digestive region, but food vacuoles are held 



