SYNOPSIS 



1 — Introduction: The Problem. 



2 — Definitions ; Length of Incubation — 



* How measured. 



** Difficulties of fixing beginning and end. 

 *** True or specific length of incubation. 

 **** False or apparent length of incubation. 

 Types of hatching — 



* Successive. 



** Simultaneous. 



3— The Data— 



* The amount. 

 ** The sources. 



*** Explanations of conflicts in. 

 **** Obvious errors in. 



4 — Influences actually or seemingly altering the specific 

 length of incubation — 



* Causing real variability. 



** Causing apparent variability. 



5 — What determines the true or specific length of incuba- 

 tion — 

 * Past Theories : 



A — The parent, or the bird itself- — 

 (a)' Its size or weight. 



(b) The age of the female. 



(c) Condition of the parents. 



(d) Faithfulness of the parents while incubating. 



(e) Longevity of the parents. 



(f ) Condition of young at hatching. 



* Precocious. 

 ** Altricial. 



*** Completeness of development at hatching. 

 B— The Egg— 



(a) Its size or weight. 



(b) Its age or viability. 



(c) Its shell. 



(d) Its yolk size. 



C — Telluric Conditions — 



(a) Zone. 



(b) Climate. 



(c) Weather. 



(d) Geographical location of species. 



(e) Site of nest. 



