REPRODUCTION IN UNICELLULAR ORGANISMS 365 



other phenomena. These forms of reproduction were long regarded 

 as the oldest and the simplest, and it is only since the time of Francis 

 Balfour that the conviction has gradually gained ground that this 

 cannot be so, but that they are rather secondary methods of multipli- 

 cation in the Metazoa and Metaphyta, which therefore rest on a very 

 complex basis. We have seen that the germ-cells made their appear- 

 ance along with the multicellular body, and the step from Pandorina 

 to Volvox is as small a step as can be well imagined. It is thus proved 

 that the oldest mode of multiplication among multicellular organisnas 

 was that thi'ough germ-cells, at least along this line of evolution. 

 Volvox does not reproduce by dividing, or by the development of 

 buds from any part of the spherical colony of cells. What is known 

 as budding among single-celled organisms is only an unequal cell- 

 division, and has nothing but its external appearance in common with 

 the budding of higher plants and animals. The latter, therefore, is 

 something new, of later and independent origin ; the priviitive mode 

 is reproduction by unicellular germs. 



