49Q POPULAR SCIENCE MONTHLY. 



it might as well be possible that the mutations were many-sided, but 

 that of them only those survived which excelled their ancestors in a 

 particular direction, better fitting them for the existing conditions. 



Finally one can come to a very important conclusion in regards 

 the manner in which plants and animals mutate. It is this, that new 

 species did not originate in a single individual, but in a number of in- 

 dividuals, either at the same time or during a number of years. Del- 

 boeuf was the first to formulate this idea, and Scott and others agree 

 with him on this point. 



This is a quite simple and natural view to take. A single indi- 

 vidual would, among all the members of his former species, practically 

 have no chance of life and reproduction, even if it were a hermaph- 

 rodite plant and much better adapted to local conditions than the 

 others. For this chance plays too prominent a part in the struggle 

 for life. There are a thousand chances that a seed does not germinate 

 or is killed in its prime, independent of any qualities it may possess. 

 Once the young plant has passed this period, the chances certainly are 

 better, but even then many succumb because they occupy an unfavor- 

 able place. But when a plant produces a number of individuals of 

 the new species at the same time, and repeats this for a number of 

 years, then the chances of the new species are sufficient; and this 

 even if it is weaker or in some regards inferior, and certainly if it is 

 as good as the mother species. It is not at all necessary that the new 

 species be stronger, or be at once offered the opportunity to make use 

 of its superior qualities. Delboeuf carefully calculated the chances, 

 but even without these calculations one can see the truth of his re- 

 marks. For the larger the number of mutating individuals, and the 

 more generations this mutating lasts, the greater will become the 

 chance of the new species to maintain itself among the old one, always 

 supposing the former is not so weak as to be crowded out each time. 

 To be better equipped than others before entering upon the struggle 

 for life is certainly a great advantage, but not a sine qua non for ulti- 

 mate success. 



Reviewing the above, we find that the mutation theory comprises 

 the following theses. Species originated from others by sudden but 

 small changes, often so small as to be hardly visible to the neophyte. 

 They are constant and true to seed from the first; neither are they 

 connected with the mother species by a series of intermediate forms, 

 nor do they have to pass in their prime, a stage of gradual develop- 

 ment. This formation of new forms does not take place continually, 

 but it is only from time to time that a species enters a period of muta- 

 bility; in this case it produces, during a certain number of years, one 

 or more, perhaps an exceedingly large number of new species. The 

 mother species itself remains unchanged ; it may persist after the muta- 



