340 Raymond Pearl 



It takes but brief consideration of these economic points to con- 

 vince one that behind them lies a very broad and complex biolog- 

 ical problem, on v^hich light must be obtained before there can be 

 any hope of solving the practical questions. This is the problem 

 of the physiology of reproduction in the hen. Egg production is a 

 definite, if complex, physiological process. In the production 

 and laying of an egg a long series of events are involved; a num- 

 ber of different organs of the body play a part. Before w^e can 

 hope to control egg production w^ith any precision or certainty it 

 is necessary to learn in detail v^hat is the normal course of events 

 in the production of an egg; hovvr and in v^hat M^ays each of these 

 events may be modified or influenced by external circumstances; 

 and to what extent each of them is an inherited matter. The 

 physiology of the organs concerned in egg production must be 

 w^orked out in detail. 



In order that a comprehensive idea may be gained of the scope 

 of this problem, let us examine the follov^ing skeleton outline of 

 the factors and processes immediately concerned in egg production 

 and the points v^hich must be investigated in attempting to get 

 light on. these processes. 



I Physiology of egg production within the individual. 

 A Processes occurring in or relating to the ovary. 



1 The development of the egg and its yolk up to the time of ovulation. 



Resorption of yolk. 



2 Ovulation proper. The rupture of the follicle. 



3 Fecundity. 



B Processes occurring in the oviduct. 



1 Movement of egg to the outside. 



2 Formation of albumen. 



3 Formation of the several egg membranes. 



4 Formation and determination of the shape and color of the shell 



of the egg. 

 C Intra-individual variation and correlations in regard to the points enum- 

 erated under A and B. Homotyposis. 

 D Behavior in its relation to egg production and reproduction in general. 



1 Mating instincts and habits. 



2 Brooding instincts and habits. 



