CHAPTER X. 

 CONFORMITY TO TYPE. 



There are few facts better recognized, yet less under- 

 stood, than that the offspring resembles its parents. 

 Such resemblance is said to be inherited, and the 

 qualities by which it is brought about, hereditary. 

 The faithful reappearance of these qualities not only 

 causes each individual to resemble its parents, but also 

 to conform to the type of its species. Failure in their 

 appearance may lead to a divergence from the parent type 

 and may result in the development of new species. 

 Heredity, therefore, is of far-reaching importance, for 

 it not only determines ontogeny, but also phylogeny. 



To those who have become reasonably familiar with 

 the reproductive processes it may not be surprising 

 that the unicellular organisms conform to their specific 

 types, seeing that each is but a portion of a preexisting 

 organism whose entire reproductive energy at the time 

 of multiplication has been directed toward securing for 

 each resulting half an exactly equal quantity of parental 

 substance. Nor is it surprising that a bud from a 

 hydra should eventually come to resemble the hydra, 

 seeing that any considerable part cut off from the hydra 

 eventually regenerates so as to return to parental 

 resemblance. But no amount of familiarity with the 

 phenomena can make the thoughtful mind cease to 

 wonder when he sees a tiny undifferentiated spore grow 

 into a beautiful fern by which myriads of new spores 

 will be produced, a very simple seed grow into a great 

 tree covered with leaves and flowers, or an egg trans- 

 formed without external assistance into a living, active 

 bird covered with feathers. That so much should be 

 potentially enclosed in a single cell, seems impossible I 



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