l88 AMPHIMIXIS OR ESSENTIAL MEANING OF [XII. 



points from that of the Metazoa, so that without first making 

 renewed investigations it is impossible to form a correct idea 

 as to what should be regarded as a ' reducing division.' 



According to my view, the explanation of the thrice-repeated 

 division of the micronucleus consists, on the one hand, in the 

 reduction of the number of idants and their arrangement in new 

 combinations, and, on the other hand, in the differentiation of 

 the two reproductive nuclei. 



Those who agree with me in looking upon amphimixis as the 

 union of idioplasms built up of ids from two individuals, will not 

 hesitate to believe that the ids are reduced to half the normal 

 number. It is impossible that there can, in this respect, be any 

 difference between the amphimixis of unicellular organisms and 

 that of Metazoa. It is not equally certain that my view of the 

 production of fresh combinations of idioplasm by means of am- 

 phimixis can be proved in the Protozoa. It might be objected 

 that it is useless for one Protozoon to possess the theoretical pos- 

 sibility of producing a great number of individual varieties of idio- 

 plasm, because each single animal is only able to utilize one out 

 of many possible combinations. The two animals which com- 

 menced conjugation remain at the end of it, and there is no 

 increase in number : hence the different nuclei which originated 

 from the ' reducing divisions ' cannot be divided among dif- 

 ferent animals, as is possible in the case of the four sperm-cells 

 which are formed b}' one sperm-mother-cell, and which contain 

 four different combinations of idants. 



This objection is easily met, for exactly the same thing 

 happens in the development of the ova in Metazoa. Just as 

 only a single &gg, w^ith a single combination of idants, can 

 proceed from each egg-mother-cell, while the other three com- 

 binations disappear in the polar cells,— so, in this case, three 

 grand-daughter-nuclei of the micronucleus disappear, and one 

 only persists. The process receives a meaning when we 

 remember that countless numbers of egg-mother-cells, con- 

 taining precisely similar combinations of idants, are destroyed 

 by the process of arranging the idants in fresh groups. 77?^ same 

 explanation holds among Infusoria; for here also countless indi- 

 viduals contain precisely similar combinations, this being true of 

 all individuals which are derived from either of the animals 

 proceeding from any one conjugation. Just as the collective 



