Eggs of the Domestic Fowl (Gallus domesticus) have been incubated by artificial means for many centuries, this technique being of course ante -dated by the natural method of the bird. Credit for the early introduction of artificial incubation is generally given to the Chinese and Ancient Egyptians who used, and still use, large earthenware ovens, heated by burning d7y manure or rice husks, to hatch chicks from fertile eggs. Landauer (1951) has described in some detail the various methods of incubation adopted in early times and has provided a very interesting history of the development of artificial incubation to modern times. The phenomenon of a hatching egg has drawn the attention of malty people through the ages for all have wondered at the ability of this biologically distinct entity to nurture within it an embryo which after the process of incubation finally emerges from the egg as a chick. Their interest has been accentuated by the fact that some eggs hatch, others do not; most produce normal chicks, some abnormal chicks. There is no knowing until the eggs have ben incubated. The aura of mystery remains but at least some of the conditions which determine the fate of incubating eggs have been wholly or partly elucidated and it is to this sphere of knowledge that the present work endeavours to add. The results of previous investigations concerning the whole aspect of hatchability have been concisely reviewed by Landauer (1951) and Taylor (1949) while previous work of special immediate interest is reviewed in close associate with and under the headings of the separate parts of this Thesis. Surprisingly little is known of the conditions prevailing in the Hen's nest and the obvious lack of interes may be accounted for by the very great efficiency of artificial incubators and the necessity for mass production methods superimposing their influence and importance. These issues dominate the present -day' scene and so it was decided, having in mind the foregoing discussion, to concentrate on the study of humidity and rate of turning as applied in artificial incubation. Arising out of this work a study of the significance of embryonic orientation just before hatching on hatchability and the hatchability of some previously accepted lethal Malpositions was carried out using a technique which as far as can be determined had not been used previously. The technique involved the X- raying of eggs prior to hatching thus enabling the position of the embryo within the egg to be observed without its sacrifice.