REACTIONS OF DIDINIUM NASUTUM. 



97 



right and left, up and down, and frequently running into each 

 other. This is especially true if they have been without food 

 for a few days. In thus rapidly swimming about in every direc- 

 tion, they cover a large space in a short time and come in 

 contact with everything that may happen to be in this space. If 

 a Didiniiun chances to swim against a Paramecium in these aim- 

 less maneuvers, the two frequently adhere to each other and one 

 soon finds a tangle of fine filaments all about the scene. The 

 whole mass, filaments and all, now moves about as one, but the 

 Paramecium disappears in the course of from one to three min- 

 utes, having been swallowed by the Didiniuui. 



t> 7 8 



FIG. 6. A large Didinium immediately after having seized a small Para- 

 nieciiini. D, Didinium; P, Paramecium; n, nucleus; c, bands of cilia; c.v., 

 contractile vacuole ; s, seizing organ, showing small granules seen at the point 

 of contact between the seizing organ and the surface of the Paramecium; t, 

 discharged trichocysts ; o.i mm., projected scale. 



FIG. 7. A specimen showing the seizing organ withdrawn and the begin- 

 ning of the process of swallowing. 



FIG. 8. A specimen in which the seizing organ. S, could be clearly seen 

 attached to the prey after it had been nearly half swallowed. This shows 

 that the seizing organ travels to the posterior end of the body during the 

 process of swallowing and in so doing no doubt draws in the prey. 



Balbiani 1 (1873, P- 363) describes this process as follows: " If 

 while swiftly turning in the water, the Didinium happens into the 

 neighborhood of an animalculum, say a Paramecium, which it is 

 going to capture, it begins by casting at it a quantity of bacillary 

 corpuscules which constitute its pharyngeal armature. The Para- 

 mecium immediately stops swimming and shows no other sign 



translation quoted from "Psychic Life of Micro-organisms," by Binet. 

 Published by the Open Court Publishing Company, Chicago, Illinois, 1889, p. 54. 



