220 University of California Publications in Zoology [Vol. 19 



source of food will not hold, since I find engulfed Ulothrix, dinoflagel- 

 lates, Pandorina, Gonium, Chlorella, etc., more common in my aqua- 

 rium than Euglena. I do find the species collectively a "lover of pure 

 water," thriving in sunshine and in a balanced aquarium. I can 

 therefore, at least conclude that increasing or maximum decay is not 

 essential to the life of the organism, and that Collodictyon is not a 

 determining factor in water pollution. 



When free swimming, Collodictyon moves forward by beautiful 

 lashings of the flagella in true tractellar style, the flagella undulating 

 as the animal circles about. It may also move backward by the 

 anterior adaxial action of the flagella, but only seems to do so in an 

 avoiding reaction. It rotates on its longitudinal axis more frequently 

 clockwise, but seemingly without cause or provocation may reverse 

 and rotate counter-clockwise. The flagella may beat back on all sides 

 of the body, closely appressed to the pellicle. It frequently, when 

 near the substratum, attaches itself by its flagella and rotates clock- 

 wise about its longitudinal axis. As to the explanation of this I am 

 in doubt. I am inclined to believe it simply a thigmotactic response, 

 possibly combined with positive geotropism; but in swimming through 

 the water when nearing an object it touches it with its flagella and 

 usually passes to one side or jostles the object out of the way if small 

 enough. 



In its feeding habits, Collodictyon is most interesting. When hungry, 

 it can be distinguished from moribund stages in which all food is 

 extruded by pseudopodial projections from the lateral groove or sulcal 

 region (text fig. A, 1-5). Prance emphasized the adhering engulfing 

 process, speaking little of the pseudopodia. I wish to emphasize these 

 pseudopodia, for I observe that they function actively whenever the 

 organism is seeking food. At these times when coming in contact with 

 Protozoa or algae which it may use for food, they are wafted to the 

 sulcal region by the flagella, or else Collodictyon aligns itself alongside of 

 its prey with the pseudopodia in contact. If an elongated filamentous 

 alga is to be engulfed, the relationship between the two is nearly always 

 with the alga lying in the groove longitudinally; but I have noticed 

 with diatoms that they just as frequently are engulfed by the end. Both 

 the flagella and the pseudopodia appear sensitive to food stimulus and 

 usually there is coordination between the protoplasm of the sulcal region 

 and the flagella, though there seems to be no mechanism for this other 

 than the primitive characteristics of the protoplasm. The process of the 

 organization of a food vacuole is a combination of circumvallation and 



