364 JULIA ELEANOR MOODY 



development of trichocyst material. On the following day this 

 individual had divided once and continued to do so normally 

 during the week it was under observation. 



2. The same experiment was tried ten minutes after division, 

 resulting in the disintegration of both fragments. The failure 

 to regenerate agrees with the results of Calkins in his experi- 

 ments on Uronychia where he found the regenerating power 

 low immediately after division. 



3. Another individual was cut six hours after division, the 

 incision being made at right angles to the long axis of the body 

 but anterior to the middle (fig. 33). The anterior fragment 

 rounded up, swam actively about and at the end of twenty-four 

 hours had entirely regenerated, although it was unusually small. 

 By the following day it had reached normal size and divided twice. 

 The posterior fragment also regenerated and divided normally. 



4. A fourth individual was cut across the long axis of the 

 body posterior to the middle, six hours after division (fig. 34). 

 The anterior fragment regenerated in twelve hours. The pos- 

 terior fragment, small and irregular in shape, gradually rounded 

 up, elongated and assumed normal form. After forty-eight 

 hours, it divided and continued to do so normally during the 

 week it was under observation. 



5. Summary 



(a) Spathidium spathula varies in length from 75. 5^ to 157. 5/x; 

 in diameter from 21 ^ to 57.5ju, the average length and diameter 

 of fifty individuals measured being 110.5m and 35. 2^ respectively. 



(b) The mouth is an elongated slit, subterminal in position, 

 extending the entire length of the truncated tip. 



(c) Imbedded in the thickened rim of the mouth, are minute 

 opaque rods, the trichocysts, which when artificially exploded, 

 are readily distinguishable from the long wavy oral cilia. The 

 trichocysts are used to paralyze Colpidium upon which the 

 organism feeds exclusively. 



(d) At room temperature, the single, terminal vacuole pulsates 

 at an average of once a minute. 



