ORIGIN OF THE DIVERSE FORMS OF ANIMAL LIFE 343 



and Pasteur it was demonstrated about fifty years ago that 

 spontaneous generation does not occur under present con- 

 ditions in this world. All animals originate from their 

 parents by means of fission, spore formation, budding, or 



FIG. 384. Amoeba showing formation of two animals from one by fission. 



eggs. Fission, consisting in the division of the animal 

 into two parts, is common among the Protozoa and occurs 

 in a few species of worms. Spore formation may be seen 

 in some of the Protozoa, such as the malarial parasite, in 

 which case the animal forms a cyst or thick coat around 



