THE UNIQUENESS OF THE INDIVIDUAL 



the examples to be considered here, it is far otherwise: to 

 describe them as Lamarckian is to open the door, not to a 

 bright theoretical illumination but to a fog of undisciplined 

 fancies. If I persist in calling them Lamarckian, it is because 

 Lamarckism happens to be the subject of the present essay. 



The two examples have been chosen for their familiarity to 

 the present writer; but the whole subject of cytoplasmic in- 

 heritance in micro-organisms and its bearing upon the problems 

 of cellular differentiation in metazoan development have been 

 comprehensively reviewed by Professor B. Ephrussi in his 

 recent Withering Lectures (1952), which should be referred to 

 for fuller information.* 



(i) The inheritance of acquired resistance to antisera in Para- 

 mecium aurelia. Paramecia may be immobilized or killed by the 

 incorporation into their culture-media of an antiserum formed 

 by injecting suspensions of whole individuals into rabbits. If 

 Paramecia are cultivated in sub-lethal concentrations of anti- 

 serum, their progeny acquire a resistance to its action under 

 conditions which (it is now known) completely exclude the 

 mere selection of the more resistant forms for propagation 

 Resistance so acquired is retained for many generations of 

 asexual fission — in some varieties, through sexual fission as 

 well — in the complete absence of the stimulus which originally 

 brought about the transformation. Evidently the antiserum 

 has initiated a heritable change. 



These phenomena have been studied in recent years by 

 Bernheimer and Harrison (1940, 1941), Harrison and Fowler 

 (1945, 1946) and Kimball (1947); most of our information, 

 however, derives from the detailed and systematic genetical 

 analyses of Sonneborn (reviews 1949, 1950) and more recently 

 of Beale(1952).t 



"^ [Nucleo-cytoplas7nic Relations in Micro-organisms, Oxford, 1953.] 

 t [The most comprehensive modern summary of this work is The Genetics 

 of Paramecium aurelia, by G. H. Beale, Cambridge, 1954.] 



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