The Fusion of Individuals 101 



even between sister individuals. 1 Locomotion and 

 form changes in Ameba are accompanied by the con- 

 tinued formation of new surface films; at least in the 

 plasmagel (Mast, '26). Some experiments in which 

 Amebse were crushed suddenly under a coverglass led 

 to the bursting of old films and within limits to the 

 formation of new ones, though it could not be ascer- 

 tained directly that the plasmalemma as well as the 

 plasmagel was broken by this treatment. This makes 

 it possible that successful fusion could be brought 

 about by happening to crush two individuals simul- 

 taneously in such a way that the crushed portions came 

 in contact with one another in the incredibly brief in- 

 terval before new surface films form. The conditions 

 for the formation of these films have been little inves- 

 tigated in protozoa; but it is known that they vary 

 widely among clones, and with changes in the inor- 

 ganic composition of the medium. 



Among the hard-shelled marine foraminifera the fu- 

 sion of pseudopodia has been often observed. Ver- 

 worn ('91) attempted to produce such fusions artifici- 

 ally without success, though he discovered fusions 

 which had occurred spontaneously. Jensen ('95) ob- 

 served fusion of separated pseudopodia, and found that 

 sister individuals (Rhumbler, '02) fused unavoidably 

 if they came into contact. But there was never any 

 significant acquirement of cytoplasm on the part of 

 one or another individual. Random individuals of the 

 same species did not unite their pseudopodia; on the 

 contrary their pseudopodia either broke or withdrew 

 whenever they actually touched one another. 



The genetic relationship among plastogamic indi- 

 viduals has been demonstrated to be exceedingly im- 

 portant in the case of shelled rhizopods. Schultze 



'Kiihne ('64), Berthold ('86), Rhumbler ('98b), Jennings ('04), author. 



