1919] Rhodes: Binary Fission in Collodictyon tricilkituni Curler 209 



cytoplasmic differentiation, however, was good. The blepharoplast and 

 evidence of a rhizoplast were emphasized by preceding Heidenhain's 

 iron haematoxylin with weak Bordeaux red for twenty-four to thirty- 

 six hours, and destaining until the chromatin was almost colorless, as 

 directed by Heidenhain. Paracarmine with aluminum chloride as 

 mordant did not yield satisfactory results. Collodictyon proved sus- 

 ceptible to neutral red and methylen blue of the intra-vitam stains. 

 It was unaffected by Bismarck brown. Neutral red after a consider- 

 able time differentiated the food vacuoles and acted somewhat upon 

 the plasma. It never disclosed a pulsating vacuole. Methylen blue 

 largely reacted upon the plasma and was not differential, possibly 

 showing up the protoplasmic vacuoles with some intensity. 



In order to section I resorted to the capside method of embedding. 

 The material was taken from the xylol-paraffine, saturated solution, 

 in the centrifuge tube, and placed in a capsule. Melted paraffine was 

 dropped in and this process was repeated successively until the material 

 was satisfactorily embedded. Sections were cut 3, 5, and 7^ thick. 



GENERAL MORPHOLOGY 



Collodictyon is variable both in size and shape. Its length is 15 

 to 60^ ; width, 10 to 40/x ; thickness, 8 to 36/*. These figures show that 

 many of the individuals I have found are smaller than those recog- 

 nized by previous observers. The typical shape of the body (pi. 7, 

 figs. 1-4) is ovoid, cordate or bifurcated posteriorly. A longitudinal 

 furrow, or sulcus, is always present, though at times showing only a 

 slight indentation, but usually evident as a deep groove on one of the 

 narrower sides. Pour equal flagella about as long as the organism 

 arise from the anterior ovoid end. Anteriorly the body is ovoid, at 

 times cordate, the sulcus extending around as an indentation. The 

 general shape is rounded or compressed in the plane running through 

 the sulcus, the nucleus and the blepharoplast. The posterior end may 

 be truncated, oval, acuminate, bifid, with the cusps pointing posteriorly, 

 curved spirally or diverging at an angle up to seventy-five degrees, or 

 with three, four, or five cusps (pi. 7, figs. 5-8) caused by secondary 

 sulci which run parallel to the primary longitudinal sulcus. Changes 

 of form are gradual except when altered by engulfed food or the 

 extrusion of undigested products. The peculiarities of the posterior 

 cusps are held by a single individual indefinitely. Few individuals, 

 if any, are exactly alike in form. 



