136 SYMBIONTICISM AND THE ORIGIN OF SPECIES 



also appears probable that in some cases the fused inicro- 

 symbiont may again resolve into a definite body. 



Obviously, it is quite impossible with our present methods 

 to determine the ultimate modifications that microsym- 

 bionts may undergo. Many factors undoubtedly are con- 

 cerned in these responses, chief of which are the prototactic 

 properties of the two symbionts involved. From the 

 observations that have been made, we are justified in 

 concluding that the modifications experienced by micro- 

 symbionts range all the way from an invisible response to 

 those in which the microsymbiont completely fuses with 

 the host cell. It is evident that we have no means of 

 detecting the presence of a microsymbiont that has thus 

 completely fused with the host cell. 



To return to the question of bacterial fusion, we might 

 ask: Is there any evidence to indicate that bacteria ac- 

 tually do fuse with each other? Although the researches 

 made in this field are of rather recent date, and perhaps 

 have not been fully verified, nevertheless, direct evidence 

 has been submitted by Lohnis and Smith ('16), Lohnis 

 ('21), Ahnquist ('22) and a few others that bacteria may 

 exhibit the fusion phenomenon. Lohnis especially has 

 investigated the behavior of bacteria, and has furnished 

 much evidence in support of bacterial fusion not only from 

 the literature, but from his own observations and experi- 

 ments as well. The fusion phenomenon of bacteria has 

 been called by Lohnis "symplasm." 



In the life cycles of bacteria, a stage develops in which 

 a number of individuals of a strain come together and 

 produce a rosette. Presently, the morphologic identity of 

 the bacteria is lost; the rosette resolves into an amorphous 

 mass or body. This amorphous body is the "symplasm." 

 Later in the course of the life cycle individual bacteria re- 

 form from the symplasm, and again take up their vegeta- 

 tive functions. 



