276 J. F. McClendon 



normal and A, bearing a horn. One of the first two daughters 

 has the horn nearer the anterior end the other nearer the posterior 

 end. After each division the horn is in a different position, and 

 we can predict the position of the horn in each generation by 

 drawing an imaginary hne bisecting the animal in the preceding 

 generation transversely. Many of the "normal" daughters were 

 kept many generations without showing any abnormality in their 

 offspring. Although one series died out in the sixth and the other 

 in the eighth generation there is no reason to believe that the horns 

 would have been lost had the series lived. Sometimes the horn 

 grew and at other times decreased in size but in the later genera- 

 tions it was as large as in the earlier. It is easy to see why such 

 deformities are seldom found in nature, for in case one is pro- 

 duced, even if the deformed individual has an equal chance with 

 normal ones of living and reproducing, after seven generations 

 less than one per cent of its offspring will show the abnormality. 

 The main difference between the results of the reproductive 

 process here and in the Metazoa is the transmission of acquired 

 characters to a small per cent of the progeny in case such charac- 

 ters do not cause the death of their possessors. To speak of a germ 

 plasm in Paramoecium without morphological evidence might 

 seem unwarranted. 



3. ON ABNORMALITIES PRODUCED BY ENCYSTMENT AND OTHER 

 CAUSES IN PARAMCECIUM AURELIA.* 



The encystment of Parameoecium putridum was described by 

 Lindner ('99) that of P. busaria by Prowazek ('99) and that of P. 

 caudatum by Simpson ('01). I have repeatedly observed Para- 

 moecium aurelia forming a thin membranous cyst in which it 

 might be confined for a week but in which it was killed by drying. 

 For this reason it might be wrong to compare these cysts with 

 those observed by others in Paramoecium. "These cysts are 

 most often seen in the interior or on the surface of bacterial zooglea 

 and I thought at first that the Paramoecia were simply entangled 

 in the zooglea, but as other Paramoecia were seen at the same 



* These observations were made at the University of Missouri. 



