36 



POPULAR SCIENCE MONTHLY 



What is the physical basis — the vehicle for the transmission of all 

 the characters large and small, from one generation to the next? 



In many minute animals and 

 plants where the individual con- 

 sists of a single cell it simply 

 divides into two, so that it is im- 

 possible to say which of the two is 

 the parent, which the offspring. 

 Heredity is here simply a process 

 of growth and division. If one of 

 these individuals is cut into halves 

 each half will regenerate the part 

 lost. Normally the whole animal 

 or plant is concerned in heredity. 

 In fact, an individual may be 

 divided in any way and each frag- 

 ment will regenerate the lost part 



-3 -2 ' " * 



3 1 1 1 I I ~~7\ y 



I "- // 



o — "V — 



Fig. 3. Galton's Regression Diagram. Hori- 

 zontal lines indicate the deviation of the average 

 of thelheight of the father and mother above or so long as the fragment Contains 

 below the race, O; the vertical lines indicate the , - ,, „„„!„„_ 



average filial deviation from the average of the l Jdl L ui U1L uucieub. 



race. In many other animals, of 



If the deviation of the sons from the average , . , , rpnrpspntativp in 



of the race equaled the deviation of the par- wnicn we nave a representative in 

 ents a line joining the various filial heights would our ponds and streams in Hydra, 

 give us the diagonal from 3 to 3. Actually the 

 line joining filial heights is the one from 2 to 2, 

 which is only two thirds as far from 00 as the 

 line 3, 3. 



buds develop at certain regions 

 and grow into a new individual. 

 Here any one group out of a large 

 number of groups of cells may 

 build up a new individual. If a 

 hydra be cut in any one of hun- 

 dreds of possible ways each part 

 will regenerate the portion lost, and 

 so form a new individual. Every 

 group of cells is here adjusted to 

 reproduce the entire individual if 

 the inhibition exercised by the 

 presence of other cells is removed. 

 The method of budding is the 

 commonest means of transmitting 

 the characters in plants. Those 

 individuals produced by buds are 

 usually exactly, or very nearly, like 



Fig. 4. Diag 

 cent, of Rei 

 are Gifted. 



ram showing the small per- 

 .atives of Gifted Men who 



