PROTOZOA 3OI 



its own. These particles are, therefore, mixed and 

 combined afresh through the amphimixis. 



Moreover, the protozoa have two nuclei. It is only 

 the smaller of these that contains the rudimentary 

 particles and mixes them in the manner described. 

 The larger one has only the function of attending to the 

 animal's nutrition, movement and respiration. During 

 the amphimixis it dissolves, and is afterwards recon- 

 structed by the small nucleus. 



As a rule there is a cleavage, and therefore a multi- 

 plication, of the protozoa that have separated after the 

 conjunction has been completed. But the chief method 

 of reproduction amongst them is non-sexual, that is to 

 say, cleavage without amphimixis. In the multicellular 

 animals amphimixis is always followed by multiplication. 

 How could the germ-cells, the only ones that can enter 

 into amphimixis in such cases, return to the bodies of 

 their bearers after the act ! If the amphimixis is to 

 have any result, two germ-cells must leave the parent 

 bodies, combine, and produce directly a new animal, 

 which will have the united rudimentary particles. 



This is how the process of amphimixis takes place in 

 the pandorina, which has no division of body and germ- 

 cells. Any cell in the cluster may in this case detach 

 itself, combine with another that has separated from 

 some other animal, and with it build up a new animal. 

 Reproduction after amphimixis is only occasional in the 

 pandorina; as a rule it multiplies sexually, as stated 

 above. 



How does the process take place in the volvox, in 

 which there are two different kinds of cells, body and 



