The Evidence from Intellectual Differences. 249 



that among plants, and among all the lower and simpler 

 groups of animals, new individuals are produced by the 

 various forms of asexual generation, as well as sexually. 

 In certain animals, such as the tunicates, this form of 

 generation is highly ' specialized, and the stolon from 

 which new individuals are budded off is a highly com- 

 plex structure, which contains cells or tissues derived 

 from all the essential organs and systems of the parent, 

 and from these the corresponding organs and systems 

 of the new individual are derived. As a rule, however, 

 the process of budding is very simple: a mass of un- 

 specialized cells at some definite point upon the body of 

 the parent animal or plant becoming converted into a 

 new individual, instead of contributing to the further 

 growth of the old. Among the lower animals, such as 

 the hydroids and sponges, the process is still more sim- 

 ple, and cells may become converted into a bud at almost 

 any point upon the body of the parent. That the pro- 

 cess of reproduction by budding is not in any way abso- 

 lutely distinguished from the process of ordinary growth 

 by cell-multiplication, is shown by the fact that an acci- 

 dent may determine which of these processes is to result 

 from the activity of a given cell. 



Comparison shows that there is, on the one hand, no 

 essential distinction between ordinary growth and repro- 

 duction by budding, and, on the other hand, none ex- 

 cept the necessity for impregnation to distinguish asexual 

 from sexual reproduction. All these processes are fun- 

 damentally processes of cell-multiplication. As none of 

 the animals with which we are thoroughly familiar re- 

 produce asexually, we are unable to make any very exact 

 comparison of the results of the two processes of repro- 

 duction in animals; but among plants such comparison 

 can be made without difficulty, and will be found to show 



