A New Theory of Heredity. 87 



reproduction, before mentioned, of heads in the body 

 of certain annelids, with the facts of serial homology, 

 as well as those of bilateral and vertical symmetry. Also 

 as the atoms of a resonant body may be made to give 

 out sound by the juxtaposition of a vibrating tuning- 

 fork, so it is conceivable that the physiological units of 

 a living organism may be so influenced by surrounding 

 conditions (organic and other) that the accumulation of 

 these conditions may upset the previous rhythm of such 

 units, producing modifications in them afresh chord in^ 

 the harmony of Nature a new species. ... It seems 

 probable, therefore, that new species may arise from some 

 constitutional affection of parental forms an aifection 

 mainly if not exclusively of their generative system." 



According to the view which I have presented a new 

 variation is caused in essentially the manner which Mi- 

 vart suggests as probable. The accumulated influence 

 of surrounding conditions, organic and inorganic, does 

 upset the previous rhythm of the physiological units of 

 the living organism, and causes them to give rise to 

 gemmules, and the tendency of the corresponding units 

 of the offspring to vary, is directly due to this consti- 

 tutional aifection of the parental forms. 



I have spoken of the egg as containing material parti- 

 cles of some kind to represent each of the hereditary 

 congenital peculiarities of the race. According to this 

 view the egg of one of the higher animals must be a 

 wonderfully complex structure. At first sight it would 

 seem as if it must be as complicated as the adult animal, 

 but a little thought will show that this is by no means 

 the case. 



In the first place, there are many structures which 

 enter into the formation of the body without being part 

 of its actual living substance. Nearly every living 



