THE GENERAL SIGNIFICANCE OF AMPHIMIXIS 221 



the lirst case the cell -bodies of the two auinials ivinaiu intact, while 

 an animal that is eaten becomes surrounded by a food- vacuole, and is 

 dissolved and digested within it. In the former case the vital units 

 (biophors) of each animal obviously remain intact and capable of 

 function ; in the second, those of the over-mastered animal are at 

 once dissolved and chemically broken up ; as biophors, therefore, 

 they cease to exist. Whether one or the other process takes place may 

 perhaps depend on whether the two animals differ greatly in size, so 

 that the smaller can be quite surrounded by the larger. 



In a former lecture I have emphatically expressed my dissent from 

 the view which interprets amphimixis as a process of rejuvenation, 

 meaning thereby a necessary renewal of life, and I need not go into 

 this again in detail : for that the metabolism can continue through 

 uncounted generations without being artiliciall}^ stimulated — that is, 

 in any other way than by nutiition — is proved by all those lowly 

 organisms which exhibit neither plastogamy nor complete amphimixis, 

 and also by the occurrence of purely parthenogenetic reproduction, 

 &c. In what, then, can the advantage lit- wliich the conjugating 

 unicellular organisms deri\'e from conjugation ? Obviously not in that 

 they impai-t to each other what each already possessed, but only in the 

 communication of something special and individual, something that 

 was peculiar to each, and becomes common to both. 



Haberlandt believed that the development of auxo-spores in 

 Diatoms pointed towards the processes which form the deepest roots 

 of amphimixis. As is well known, the hard and unyielding flinty 

 shell of these lowlv Algfe involves a diminution of the orp-anism 

 at every division, so that the Diatoms become smaller and smaller 

 as they go on multiplying, and if that went on without limit they 

 would come rapidly to extinction. But a corrective is supplied in the 

 periodical occurrence of conjugation of two organisms which have 

 already materially diminished in size, and this is followed by the 

 growth of the two fused individuals to the original normal size of 

 the species. 



It is, of course, obvious that in this case the union of two 

 organisms which have become too small may be of advantage 

 in bringing them back to the requisite normal size ; but this is an 

 isolated special case, which certainly does not justify our regarding 

 conjugation as a means whereby diminished bodily size may be brought 

 Ijack to its normal proportions. By far the greater number of unicel- 

 lular organisms are not permanently diminished in size by division, 

 and even in the Diatoms the mass of the two fused individuals does 

 not amount to the normal size of the species, so that even in this 



