INHERITANCE OF ACQUIRED CHARACTERS 163 



or America increases in size as the result of a better food 

 supply. 



Woltereck, by changing the food supply only, in hyalo- 

 daphnia, succeeded in changing the percentage of the 

 height of the head to that of the body from 40 to over 90. 



The remarkable influence of the amount of food supplied 

 to an animal during its development in modifying the 

 somatic cells and changing the external form of animals, 

 is well illustrated by the unpublished results of an experi- 

 ment conducted at the Missouri Experiment Station. 1 

 In this investigation, the animals were maintained for 

 long periods upon different planes of nutrition. 



For the purpose of this investigation the animals were 

 divided into three groups. Group one (see Plates VII, 

 VIII and IX) was supplied with a generous ration cal- 

 culated to furnish to the animal all the nutrients it 

 could utilize, and produce the maximum growth and 

 development, including the laying on of fat. The treat- 

 ment given to group one resulted not only in very 

 rapid growth and development, but as the excessive 

 feeding was long continued, the animals laid on unusual 

 and excessive amounts of fat. 



The ration supplied to group two (see Plate VIII, 

 lower) was intended to provide such a quantity of food 

 as was sufficient to produce strong, healthy growth and 

 development, but insufficient for laying on any consider- 

 able amount of fat. This ration resulted in normal, 

 healthy growth, but the food supplied was constantly 

 below the desires and appetites of the animals. There 

 was no time during the experiment at which the animals 

 would not have consumed more food. 



1 Waters and Trowbridge, Unpublished Data from the Mis- 

 souri Experiment Station. 



