MATERIALS OF HEREDITY 7 



lized egg. And this fertilized egg is the beginning of the 

 new Individual. 



In most organisms, as we know, these two minute pieces, 

 the sperm and the egg, form the only connection there is 

 between parents and offspring. This Is not true in some of 

 the higher organisms, such as man, but It Is true In most 

 organisms. It Is therefore clear that in such organisms 

 all relationship between parent and offspring is through 

 these minute bits of material, the germ cells. It is on them 

 that it depends whether the new individual shall be a snail, 

 a fly, a fish, a frog, a bird. 



It has since been discovered that the same is true even 

 In animals in which the mother carries the young in her 

 body for a time. This remaining In the body of the mother 

 has very little effect on the nature of the individual pro- 

 duced. It depends on the material of the two minute cells, 

 the sperm and the egg, whether there shall be produced a 

 dog, a horse, or a man. And If a dog is produced. It de- 

 pends on these whether It shall be a hound, a bull-dog, a 

 spaniel, a poodle, or some other variety. In man it depends 

 on these two pieces of material whether the child produced 

 shall belong to the black or yellow or white race. And on 

 them depend in large measure the form, the size, the type 

 of features, and even the physiological and mental char- 

 acteristics. On them depend the resemblances that the child 

 shows to Its parents in all these respects; and on them also 

 depend to a large degree the differences between one indi- 

 vidual and another. Practically everything that brings about 

 the relation of parents to offspring therefore lies in these 

 two minute bits of material. They are obviously of ex- 

 treme importance and interest, so that men set to work, 

 a long time ago, to examine them with microscope and 

 with all other means at their disposal. And in the course 

 of time they found out many extraordinary things about 



