12 THE FIRST PRINCIPLES OF HEREDITY 



This process of simple fission is the most common 

 method of propagation among the Protozoa and Proto- 

 phyta, but it can also be observed in species of higher 

 organization, even as high up as the worms. 



So we find among the Polypes some which multiply by 



division ; the newly - formed 

 <8$&mJ^ M*g individuals, however, do not 



separate, but remain attached 

 to each other, thus forming 

 what is called a Polype - 

 stock. 



Among the worms, we have 

 the Bristle-footed worm 

 (Chcetopoda) , which, either on 

 a shock or normally, breaks 

 up automatically into several 

 pieces. The sea- worm Myri- 

 anida forms, when dividing, a 

 whole chain of young worms. 

 In both these cases it is evi- 

 dent that after the division of 

 the mother-animal the com- 

 pletion of the daughter-worms 

 must take place by regenera- 

 ting the missing portion of the 

 the body, either fore- or hind-end, 

 or both. Here, too, we can 

 still trace the close connection 



between the process of reproduction on the one hand and 

 that of growth and regeneration on the other. 



FIG. 3. DIVISION OF AMCEBA. 



(From Weismann, " The Evolu- 

 tion Theory.") 



A , before division ; B, the 

 nucleus divided ; C 

 daughter amoebae. 



(b) Budding. 



While in division, as just described, the whole mother- 

 organism enters into the formation of the respective parts 

 of its progeny the parent-animal thus being lost in, or 

 rather merged into, its own descendants in budding the 



