40 THE BIOLOGICAL PROBLEM OF TO-DA Y 



addition to their patent characters, contain latent 

 characters which have reached them by doubling 

 division, and which are representative of the 

 species. 



i 



FIRST GROUP OF FACTS. UNICELLULAR ORGANISMS. 



Doubling division alone exists, or could exist, 

 among unicellular organisms. The maintenance of 

 the species depends upon this. Our belief that a 

 species produces only its own species, that like 

 begets only like, a belief that finds continual con- 

 firmation all through the study of systematic and 

 embryological natural history, would disappear, were 

 it possible that in the division of unicellular organ- 

 isms the hereditary mass should be split into two 

 unequal components and be bestowed unequally 

 upon the daughter-cells. All research shows that 

 unicellular fungi, algae, infusoria, and so forth, in 

 dividing, transmit specific characters so strongly and 

 in detail so minute that their descendants, a million 

 generations off, resemble them in every respect. 

 No one has doubted the fact, and Weismann him- 

 self recognises that division, among unicellular 

 organisms, is always doubling. The process of 

 division, as such, appears never to be the means by 

 which new species are called into existence among 

 unicellular organisms. This is a fundamental pro- 

 position of cell-life, not to be doubted, and to be 

 taken into account in the presentation of theories 

 of heredity. 



From the proposition that like begets only like 



