ZOOLOGY 



Dominance 

 of the 

 hereditary 

 factors 



seems that we 

 started in busi- 

 ness with very 

 little capital, 

 and have be- 

 come almost 

 everything we 

 are by taking 

 advantage of 

 the environ- 

 ment. In our 

 original phrase, 

 it seems to be 

 nearly all nur- 

 ture and very 

 little nature in- 

 deed. 



3. We notice, 

 however, that 

 we are human 

 beings, and that 

 the offspring of 

 such are always 

 human. So also 

 the progeny of 

 elephants are elephants, of cabbages, cabbages. Why 

 should this be so, if the environment is the principal 

 thing? Heredity appears to contribute to the elephant 

 a single minute mass of protoplasm of microscopic size ; 

 the whole vast body is built up out of the nourishment 

 secured ; should the latter not determine the size, 

 form, and quality ? On the contrary, the microscopic 

 cell decides not merely that the creature shall be an 

 elephant, and no other sort of beast, but also what 



Photograph by W . M. Goldsmith 



FIG. 20. Two lots of potatoes raised by Mr. William M. 

 Goldsmith at Gunnison, Colorado, in 1918. Both had the 

 same parentage, but one lot'was propagated from the larg- 

 est tubers in the hill, and the other from the smallest. 

 Similar tubers are shown at the base of each bucket. 

 Both lots were given the same treatment. The yield 

 shown in the buckets was 25 and 27 Ibs., respectively, 

 showing no superiority in the product of the large tubers. 

 Potatoes are reproduced vegetatively from the tubers 

 without change in hereditary qualities, except in the rare 

 case of a bud sport or mutation. The experiment illus- 

 trates the non-inheritance of acquired characters. The 

 little tubers were little because of differences in time of 

 development or position, broadly speaking of nutrition, 

 and not because they had inherited different qualities. 

 There are, however, other forms of the potato genus 

 which have invariably small tubers, and these will repro- 

 duce nothing larger, being controlled by heredity. 



