FEEDING REACTIONS IN DILEPTUS GIGAS. 127 



period, depending upon various 'conditions. It then reacted nega- 

 tively with great vigor, and simultaneously or occasionally after a 

 very brief latent period, it bulged out in the center and went 

 through the typical euglenoid contractions with great vigor, some- 

 times holding the contracted form for two or three minutes. If, 

 immediately after the first reaction, it failed to get out of the oral 

 current which is continuously produced by the band of cilia on 

 either edge of the flattened surface of the proboscis, it was carried 

 to the mouth a*nd engulfed (Fig. 2, b). If, on the contrary, the 

 first reaction carried it outside the influence of the oral current, it 

 began after a short interval to show some activity and soon recov- 

 ered, unless it again came in contact with the proboscis. If this 

 occurred, it was almost always carried to the oral region and 

 engulfed. 



The process of engulfing was quite extraordinary. Whenever 

 the oral current carried a euglena to the mouth, the gullet, appar- 

 ently owing to mechanical stimulation, protruded so that a mass of 

 viscous protoplasm was exposed (Fig. 2, c}. If any particle came 

 in contact with this it adhered, and when this occurred the gullet 

 was again drawn in carrying the particle with it (Fig. 2, d, e). In 

 this process there was apparently some suction, for considerable 

 water was always taken in with the solid particles (Fig. 2, /). 



These observations were repeated on many favorable occasions, 

 and, furthermore, are substantiated in the main by a similar obser- 

 vation recorded by Wrzesniowski ('70). Referring to the capture 

 of a Stylonychia by Dilcptus, Wrzesniowski says, " it tries by 

 means of its proboscis to bring it down into its occasionally wide 

 open mouth, whereupon the protruding lips seize so firmly upon 

 the captured little animal that the latter is bitten in two." My 

 observations agree with only the first part of this quotation; the 

 idea of biting is quite contrary to the results of any observations 

 which I have made. 



B. ROTIFERS. 



In the observations on feeding on rotifers described below, nine 

 specimens were added to a small amount of water containing about 

 twenty starved dilepti. Within two minutes all the rotifers were 

 attacked. The dilepti appeared to sense ( ?) the rotifers while still- 



