VARIATION AND HEREDITY 



163 



a protozoan at the time of nuclear reorganization either by 

 division, conjugation, or by endomixis, they may bring about 

 long-lasting modifications (JoUos) or mutations. In Popoff's ex- 

 periment with Stentor and in Chatton's with Glaucoma, both 



Fig. 80. Varieties of Ceratium hirundineUa from various European 

 waters (Schroder), a, /?trcoiV/es-type (130-300/i by 30-45/x); b, brachy- 

 ceroides-type (130-145)u by 30-45ju); c, silesiacurn-type (148-280/i by 

 28-34^i); d, carinthiacum-type (120-145/i by 45-60ju); e, gracile-tyTpe 

 (140-200M by 60-75ju); f, aiistriacum-type (120-160/x by 45-60^); g, 

 robustum-type (270-310/i by 45-55ju); h, scotticum-type (160-210ju by 

 50-60m); i, piburgense-type (180-260^ by 50-60^). 



conducted during the asexual division, long-lasting modifications 

 have appeared in the experimental animals. Calkins (1924) ob- 

 served a double-type Uroleptus mohilis which was formed by a 

 complete fusion of two conjugants. This abnormal animal divided 

 367 times, living for 405 days, but reverted into normal forms 



