FACTS AND PACTOR-S OF DEVELOPMENT 9 



egg, by a male sex cell, or spermatozoon. The 

 epigram of Harvey, "Omne vivum ex ovo" 

 has found abundant confirmation in all later 

 studies. Both egg and spermatozoon are alive 

 and manifest all the general properties of liv- 

 ing things. How httle this fact is appreciated 

 by the public is shown by the repeated an- 

 nouncements by the newspapers that "Profes- 

 sor So-and-so has created life because he has 

 made an egg develop without fertilization." 

 An egg or a spermatozoon is as much alive as 

 is any other cell; as characteristically alive as 

 is the adult animal into which it develops. 



It is difficult to define life, as it is also to de- 

 fine matter, energy, electricity, or any other 

 fundamental phenomenon, but it is possible, to 

 describe in general terms what living things 

 are and what they do. Every living thing 

 whatever, from the smallest and simplest 

 micro-organism to the largest and most com- 

 plex animal, from the microscopic egg or 

 spermatozoon to the adult man, manifests the 

 following distinctive properties: 



(a) It contains protoplasm, "the material 

 basis of life," which is composed of the most 



