1919] Rhodes: Binary Fission in Collodictyon triciliatum Carter 203 



Body obtusely pyriform or subcordate, widest and rounded anteriorly, taper- 

 ing towards and bluntly pointed at the posterior extremity, about one and a 

 half times as long as broad; a deep groove traversing the entire length of the 

 centre of the ventral side and imparting to the posterior extremity, as seen 

 from beneath, a bilobate contour; flagella four in number, of equal length, 

 inserted close together in the centre of the anterior border; endoplast and 

 contractile vesicle located side by side near the same anterior margin; par- 

 enchyma granular, soft and plastic. Length 1/700. Hab., fresh water. 



Biitschli (1887, p. 841) recognized these two forms as the same 

 and Tetramitus sulcatus Stein as a synonym of Collodictyon triciliatum 

 Carter, characterizing the genus as follows under the family Tetra- 

 mitina : 



Massig gross (L. bis 0,035 Mm.), estalt vorn etwas verbreitert und quer 

 abgestutzt, nach hinten wenig verschmalert und abgerundet. Wahrscheinlich 

 etwas abgeplattet; iiber die eine Flache zieht eine breite Langsfurche hinab. 

 Vorderende mit vier gleich langen aus einem Punkt entspringenden Geisseln 

 (Carter gibt nur drei an). Nucleus und contractile vacuole im Vorderende. 

 Nahrungsaufname sicher. Vermehrung durch Langstheilung. Siisswasser. 

 Europa und Ostindien. 



In 1893 Klebs investigated a form which he designated as Tetra- 

 mitus sulcatus Stein. He found the four flagella of unequal length 

 and a contractile vacuole in the posterior end of the body, the longi- 

 tudinal furrow a spiral, the size being 17 by 15 microns. These differ- 

 ences lead me to conclude, after careful consideration of his descrip- 

 tion and figures, that he is mistaken in his verification and the form 

 he described is not Collodictyon triciliatum, but probably some species 

 of Tetramitus. 



France (1899) studied Carter's organism thoroughly; his descrip- 

 tion is accurate and detailed, his figures typical and true to life. My 

 own observations coincide with his in practically all details. He con- 

 cluded that Klebs' (1893) description was not of Collodictyon. He 

 dealt fully with the morphological features and metabolic changes, to 

 which I have little to add. In only one important point do our 

 observations fail to agree. I can find no contracting vacuole. He left 

 untouched, however, the method of mitosis, merely stating that repro- 

 duction was by longitudinal division, which was also noted by Carter 

 (1865) ; it is to this especially that I shall address myself. 



I am indebted to Dr. Olive Swezy for suggesting the desirability 

 of working out the mitosis of this form, the correction of the bibli- 

 ography, sketching figures 75, 78, and 83 of plate 8, in my absence, 

 and for repeated criticism and help. I also wish to thank Professor 



