THE CONSERVATION OF LIFE 241 



having become divided into numerous parts which still further 

 divide into smaller particles until from 500 to 600 nuclei have 

 been formed. Around each of these minute nuclei a part of the 

 protoplasm becomes aggregated, and now the cyst is inhabited, 

 instead of one mother-amoeba, by many thousands of minute 

 amoebae of about O'Ol to 0'015 millimetres. Very soon the entire 

 company leaves the protecting shell, enters the outer world, and 

 grows gradually into normal amoebae. 



It will be noticed that here, as in other cases mentioned, the 

 mother-amoeba does not become entirely dissolved into her 

 descendants, for a considerable part of the maternal protoplasmic 

 body remains as residue in the cyst ; but though doomed to rapid 

 decay we cannot call it a ' corpse.' The entire process as 

 described has taken about three months. 



If we have not been able to become here acquainted with 

 all the details of the evolution of the protozoans we have at any 

 rate learned the most essential factors. It is now necessary 

 to answer one important question : How did the higher animals 

 develop from the unicellular organisms ? Which causes brought 

 about a combination of numerous cells into a higher organic unit, 

 a multicellular organism ? Are there any connecting links be- 

 tween the protozoa and the strange world of metazoa ? These 

 are questions which force themselves upon us and demand an 

 answer. 



Like protozoa and the lowest plants, all multicellular or- 

 ganisms consist at the starting point of their individual existence 

 of one cell, the fertilized ovum. Like a protozoon, the egg-cell 

 multiplies by simple fission, and thus gives existence to number- 

 less descendants. And yet what an enormous difference in their 

 future fate ! While both daughter-individuals of a protozoon 

 completely separate one from the other, and after fission exert 

 no influence whatsoever upon their mutual development but 

 develop into individuals which are equivalent to the mother- 

 organism in every detail of organization and able to proceed 

 after a short time to the reproduction of similar descendants, the 

 future destiny and appearance of the young offspring of the ovum 

 is very different. 



In contrast to the daughter-cells of the protozoon, the 

 descendants of the ovum remain, even after fission, permanently 

 connected, and retain a far-reaching influence upon each other. 



16 



