28 M. L. Shorey 
The work of the two last investigators has been published since, 
or about the time that I began to investigate the relation of nerve 
and muscle tissue in the chick embryo, and did not reach my 
hands until a later date. ‘The experiments to be described were 
undertaken for the purpose of studying the behavior of the develop- 
ing nervous system,when it is itself left quite intact and with all its 
relations normal except that a peripheral area to which nerves 
should be distributed is destroyed. 
The work was begun at the suggestion of Professor Frank R. 
Lillie, and I wish to express my indebtedness to him for proposing 
a problem which has proved to be of intense interest, and for 
suggesting the first methods by which it was to be attacked. I 
wish also to express my appreciation of his continued interest and 
helpful criticism. Acknowledgments are also due to Professors 
C. O. Whitman, C. M. Child, and W. L. Tower for suggestions in 
regard to illustrations, photography and material, and to Miss 
Sabella Randolph, Mr. Kenkichi Hayashi and Mr. C. E. Brues 
for aid in the preparation of drawings and photographs. Figures 
36 and 37 are copied from Lillie’s Embryology of the Chick. 
il EXPERIMENTS (ON THE CHICK 
A Chotce of Material 
The chick embryo was chosen as furnishing a form favorable 
for these experiments; the work of Lillie (’04) in destroying various 
portions of the embryo had shown that no regulation or regenera- 
tion was to be expected and my own work has entirely confirmed 
these results. After two days of incubation, the earliest period at 
which I have operated, and in regions where no differentiation is 
apparent, the primordium for each organ 1s so definitely laid down 
that the destruction of it, or any considerable portion of it, results 
in a corresponding loss in the fully formed animal. Lillie’s work 
had also shown that comparatively large areas may be destroyed 
without interfering with the normal development of the rest. It 
would therefore be possible to destroy the primordia of definite 
muscles, or of sensory areas, before they had been penetrated by 
nerve fibers, and then determine the course of the nerves which 
