60 



SYMBIONTICISM AND THE ORIGIN OF SPECIES 



ships of the various end results in the expression of the 

 principle of prototaxis: 



Prototaxis' 



Positive 



Conjugation 



Symplasm 



Symbiosis 



Cell fusion 

 (in tissues) 



Temporary 

 Permanent 



Intracellular 



[incomplete 



I Absolute (Symbion- 

 [ ticism) 



[incomplete 

 Extracellular^ 



[Absolute? 



[intracellular 



Parasitism 



1e 



Extracellular 



Negative 



Conjugation has been observed, chiefly, in the protozoa 

 or one-celled animals. It consists of a temporary, in some 

 cases permanent, union of two individuals of a species. In 

 the Paramecium, for example, two individuals come to- 

 gether and remain attached for a short period of time. 

 During this attachment certain internal changes occur, 

 and an interchange of some materials of the two conjugat- 

 ing individuals takes place. Conjugation in the bacteria 

 has been described by Lohnis ('21) and others. On account 

 of the small size and the mode of life of the bacteria, 

 conjugation in these forms is not so readily detected as in 

 the larger protozoa. Lohnis has submitted a number of 

 photographic illustrations of bacteria in the state of con- 

 jugation to support his claim that bacterial conjugation 

 does occur. 



