A New TJieory of Heredity. 93 



win quotes from Dr. Edmonston the statement that a 

 similar change occurs twice a year in the stomach of an- 

 other, sea-gull in the Shetland Islands, where this bird 

 frequents the corn-fields and feeds on seeds in the spring, 

 but catches fish during the rest of the year. This 

 observer has noticed a great change in the stomach of 

 a wren which had long been fed on vegetable food; and 

 Menetries states that when an owl was similarly treated 

 the form of the stomach was changed, and the inner 

 coat became leathery, while the liver increased in size. 

 Semper states that Dr. Holmgrin has been able to trans- 

 form the gizzard of a pigeon into a carnivorous stomach 

 by feeding the bird on meat for a long time. 



There is no reason for believing that the few cases 

 known to us are all which are due to the direct action of- 

 external conditions, and we must acknowledge that there 

 may possibly be many structural characteristics of animals 

 and plants which are not hereditary, but are constant 

 simply because the conditions which cause them are con- 

 stant, and as we are only compelled to attribute to the 

 ovum representatives of all the hereditary race charac- 

 teristics, it will be seen that the structural complexity 

 of the egg may be vastly less than that of the developed 

 organism. 



This is not all, however. There may be many con- 

 genital race characteristics which are not hereditary. 



The various parts of a developing organism are exposed 

 in countless ways to the influence of other parts. The 

 simplest illustration of this fact is the mechanical pres- 

 sure exerted upon each other by the developing viscera. 



This is a subject which is almost outside the province 

 of experiment, for we cannot shut out the influence of 

 any particular organ without removing the organ itself, 

 and the removal of any organ of considerable size is 



