800 MORPHOGENESIS 



further investigated by Bauer and Granowskaja (1934b) in Oxytrkha. 

 Operations made subsequent to division, but before the end of the growth 

 period, hastened the next division. When operations were made a short 

 time before the appearance of division symptoms, regeneration sup- 

 planted division. Repeated operations of this kind had the effect of 

 shortening the interdivisional period and, as a consequence, the succes- 

 sively operated oxytrichas progressively diminished in size until death 

 occurred. The cytological and some of the physiological aspects of re- 

 organization are given in a preceding publication (Bauer and Granow- 

 skaja, 1934a). Luntz (1936) suppressed division in Stylonychia sp. by 

 subjecting these organisms to weak electric currents (0.95-1.0 ma and 

 2.0 a, voltage not stated) for approximately one hour each day. Divi- 

 sion was averted for a period equal to twenty-seven to twenty-eight con- 

 trol generations, but each application of the current was followed by a 

 transitory diminution in cell size. 



The substitution of regeneration for division is suggestive, but does 

 not prove that the vitality or longevity of the undivided cell is thereby 

 increased. It is known that Protozoa which, for some reason, fail to 

 divide for relatively long periods become morbid. Agonal symptoms 

 and death are the usual accompaniments of the depression. But we have 

 not yet succeeded in experimentally inhibiting division in a cell by means 

 other than surgery without inducing adverse changes in its physiological 

 behavior. It is significant, nevertheless, that physiological reorganiza- 

 tion has been detected in a variety of species after mechanical injury, 

 exposure to irritants, or during periods of starvation. The internal 

 changes induced by these conditions appear to be restorative rather than 

 adaptive. 



More information is necessary before we can be confident of the 

 conditions governing the mode of injury repair, whether by divisional 

 or physiological reorganization. The nuclear and cytoplasmic alterations 

 accompanying division have been studied extensively. On the cytological 

 side, the reorganization processes in ciliates are most profound in the 

 hypotrichs; and, as has been mentioned already, relatively small injuries 

 often provoke a complete cycle of de- and redifi^erentiation. In the less 

 specialized types, the internal changes at division are less striking. Ac- 

 cording to many observations, some of the parental organelles are passed 

 unchanged to one or the other of the two daughters. It is in the hypotrichs 



