132 DOMESTICATED ANIMALS AND PLANTS 



shows the importance of early food and care for the young of 

 our domesticated species. 



Plants are easily dwarfed, either by scarcity of food or by 

 repeated planting of immature seed. Many species have their 

 dwarf varieties, though others are artificially produced by graft- 

 ing on other and smaller species, as, for example, the pear, 

 which is dwarfed by grafting upon stock of the quince. 



Overdevelopment, or giants. In normal development and 

 differentiation, growth should not only proceed to the proper 

 point, but it is fully as important that it stop at that point. If it 

 does not, then overgrowth takes place and a giant is produced. 



As the dwarf is the result of too little cell division and too 

 few cells, so the giant is the product of too much cell division 

 and too many cells ; that is to say, of growth that did not stop 

 at the right point. 



Giants are common in man and frequent in cattle. So far as 

 is known to the writer, they are unknown in horses, sheep, and 

 pigs, though these species can all be increased in size somewhat 

 above the normal by extreme feed and care in early life as well 

 as by selection of parents above the normal. 



Neither giants nor dwarfs possess special interest to the 

 improver, because if we needed a smaller or a larger race than 

 the normal, we should not depend upon these occasional indi- 

 viduals, which are abnormal, to produce it. Their mention here 

 is for the purpose of making the student somewhat intelligent 

 on the processes of life, to do which requires a number and 

 variety of examples involving various phases of abnormal 

 development. 



Arrested development of a single character or part. Dwarfing 

 may take place with respect to one or more parts or characters, 

 while others proceed to normal development, giving a more or 

 less distorted body. 



This form of abnormality has many manifestations. In some 

 cases, for example, a part is entirely missing, as if the unit char- 

 acter had been lost, as in a case, known to the writer, of a man 



