#1. The investigation was designed to gain information on the role of the three main components of the egg (yolk, albumen and shell) in determining its total weight., with special reference to the variability known to occur when eggs are produced in sequence. #2. The data used consisted of weight measurements made on the whole egg yield of twelve purebred Brown Leghorn pullets from 4th March 1947 to the end of their respective laying cycles. #3. Clutches examined varied in content from 2-6 eggs; the first two classes contained more than halfihe total eggs and the last three slightly under a quarter. #4. The overall mean egg weight was 60.78 grams It 0.258 and the respective corresponding percentages of yolk, albumen and shell, 31.0, 59.7 and 9.4%. #5. The trend for whole egg weight is downward with successive position in the clutch and increasing clutch length; the differences become progressively smaller; that between the first and second egg of the first two clutches is disproportionately large. Egg weight increases as the season under review advances. #6. Yolk and albumen weights showed the same trends to varying degrees. #7. In shells, mean weight fell with increasing clutch size but in the other two groupings (clutch position and season)ruirecse the order found in the first two components, except that in the 5 and 6-egg clutches, the last, first and second eggs were heaviest. #8. Correlations between yollf and albumen weight were significant and positive for the first part of the season under review, but in four birds this relation broke down in the second part. Compared with those which behaved consistently, the eggs from this group showed a slightly larger increase in yolk weight in the second seasonal period, a noticeable lack of increase in albumen and a marked decrease in shell weight. 9. The data on yolk conforms with the views that delayed ovulation increases the weight of the first egg of a clutch and that changes in size may be hormonally controlled. #10. It was concluded that two major factors may affect albumen variations (a) the changing size of a mechanical stimulus consisting of the yolk plus the soluble proteins secreted between the passage of one egg and another, and (b) the time the egg remains in the uterus. #11. Shell variations could be related to the time interval between /- between ovipositions and so to the length of sojourn in the uterus. #12. A final inference is that though sources of stimulation such as hormones, might be expected to increase egg weight through an effect on time of ovulation and the secretion rate of soluble proteins, a possible negative relation between yolk weight and time of oviposition might result in a limiting effect on albumen and shell secretion. The question of the actual relations obtaining between ovulation and oviposition therefore, seems to be vital to any attempts to increase egg size by artificial means.