A New Theory of Heredity. 93 



win quotes from Dr. Edmonston the statement that a 

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

 other sea-2:ull in tlie Sliethmd Ishxnds, where this h'ird 

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

 hut catches fish during the rest of the year. This 

 ohserver has noticed a great change in the stomach of 

 a wren which had long heen fed on vegetahle food; and 

 Menetries states that wlien 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. Ilolmgrin 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 tlie structural complexity 

 of the ^g% may be vastly less than that of the developed 

 oro'anism. 



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

 gou it d 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 ])articular organ without removing tlie organ itself, 

 and the removal of any organ of considerable size is 



