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. 



