228 UNIVERSITY OF MISSOURI BULLETIN 



Gregor Mendel, in the garden of his monastery at Briinn, was 

 quietly carrying out a series of experiments in crossing dif- 

 ferent varieties of peas — experiments which were destined 

 many years later to startle the scientific world. His results 

 were published in 1865 in a brief paper which appeared in the 

 proceedings of a local natural history society, and there they 

 remained absolutely unnoticed until they were unearthed in 

 1900. The great and fundamental value of the principles which 

 he had deduced from his experiments, now known as Men- 

 del's Law, was at once widely recognized and within the past 

 ten years his results have been repeatedly confirmed and 

 shown to hold good for animals as well as for plants. Upon 

 the foundation thus laid by Mendel, the modern science of 

 genetics has been built, and the law which he enunciated with 

 such astonishing clearness has made possible for the first 

 time a precise analysis of hereditary phenomena. 



Since the individual animal or plant arising in the sexual 

 process of reproduction is the outcome of the union of two 

 germ cells or gametes which are formed in the bodies of 

 the two parents, respectively, the characters which are peculiar 

 to it must in some way be represented in the egg cell and the 

 sperm cell. By observing how and in what proportions the 

 characters of the parents reappeared in the offspring, when 

 individuals diflfering by certain contrasted pairs of characters 

 were interbred, Mendel was led to the conception of unit 

 characters in inheritance, or characters which are transmitted 

 through the germ cells as whole, unsplitable units. And, fur- 

 thermore, the results of his experiments were only explicable 

 on the assumption that the physical basis or determiner for 

 each member of a pair of contrasted units was borne in a 

 separate germ cell. In other words, the germ cell is pure for 

 that character. The determiners of heritable unit characters 

 are, therefore, said to segregate in the gametes, and it is this 

 simple conception of "segregation" that has furnished the 

 clue by means of which we have been led to a precise analysis 



