422 University of California Publications in Zoology [Vol. 19 



MICRONUCLEUS 



This organelle is much less conspicuous than other organs in living, 

 unstained animals, but when once clearly identified it may always be 

 readily located with suitable magnification and properly regulated 

 light. The variations in position and size depending upon its several 

 phases (Yocom, 1918) have been defintiely verified even without the 

 aid "f vital dyes. With a .0001 per cent aqueous solution of neutral 

 red, haematoxylin, methylene blue or Bismarck brown, both micro- 

 and macronucleus become sharply outlined and the visibility of their 

 structure is considerably enhanced. Several times the macronucleus 

 has been dissected out with the micronucleus attached and lying in a 

 very shallow pocket (Griffin, 1910; Yocom, 1918). In two cases, the 

 micronucleus was brushed with the needle-point out of the depression 

 in which it was feebly held evidently by a viscous, ductile substance 

 that stretched only for a few microns in fine, retractile threads. These 

 properties of this substance indicate that it may be comparable with 

 the hyaline, gelatinous matrix of the macronucleus. Other interesting 

 features of the micro- and macronucleus will be treated in a later 

 paper. 



Contractile Vacuole 



My observations on the size and position of this organelle are in 

 general agreement with Yocom 's (1918), although I have observed an 

 abnormal increase in its size after certain vital stains such as neutral 

 red, Bismarck brown, Congo red, gentian violet, fuchsin S, etc.. have 

 been added to the water. Moreover, any distinct mechanical disturb- 

 ance, e.g., rapid movement of the needle to and fro through the hang- 

 ing drop, continually jarring or shaking the moist chamber, etc., 

 effects very noticeable changes in the size and period of pulsation of 

 the vacuole. One should then expect, as is the case, that incisions, 

 transections, or excisions would similarly affect this organelle. It 

 would appear, indeed, that the contractile vacuole in Euplotes patella 

 is exceedingly sensitive to various stimuli. The average size of this 

 vacuole in ten carefully handled animals was 29 microns at maximum 

 diastole. Its diameter upon disturbance or after incisions may become 

 45 or even 50 microns, and its period of pulsation, which is normally 

 about forty seconds between systoles, may thereupon vary from three 

 to fifteen minutes. 





