246 THE UNFERTILISED EGG AS A [pt. iii 



again. Malcolm maintained in 1902 that, although there were un- 

 doubtedly differences between the eggs of different breeds of hen, 

 they did not exceed the amount of variation between individual eggs 

 from hens of the same breed. His results are shown in Table 3. 

 Thus, although the feeding was carefully controlled, the eggs 

 from one hen might show a difference of i'i4gm. of fat, while 

 between two eggs from different breeds the difference might be only 

 0-13 gm. His conclusions were supported in the main by Carpiaux; 

 Leveque & Ponscarme ; von Czadek ; Iljin ; and Willard, Shaw, 

 Hartzell & Hole; who made very long studies of a considerable 

 number of breeds. Some of the figures obtained by von Czadek 

 and Iljin are given in Table 5. Von Czadek studied the Sulmtal, 

 Minorca, Orpington, Rhode Island, Faverolle, and Wyandotte 

 races, together with an Italian and a Rhineland breed. His outside 

 values for egg weight, for instance, were 43 gm. and 75 gm. — 

 a considerable difference — but the former was from the Rhineland 

 hen and the latter from the Minorca variety. The span showed great 

 variations, thus an egg weighing 55 gm. might be a heavy Orpington 

 or a rather light Faverolle or a medium weight Italian. The only 

 breed which stood well out of the range of individual differences was 

 the Minorcas which laid very heavy eggs. Certain instances have 

 shown, however, that remarkable agreement may exist between work 

 done on eggs of widely different breeds. Thus the classical work of 

 Plimmer & Scott on the phosphorus metabolism of the developing 

 chick was confirmed very strikingly by Masai & Fukutomi, who 

 worked in Japan. Here the correspondence was almost numerical. 

 But on the other hand there is evidence that eggs of different breeds 

 differ not only in their gross characteristics, but also as regards more 

 subtle properties; thus Moran has demonstrated that eggs from 

 different breeds of hen vary very greatly in their resistance to cold, 

 so that the viability is different, and Needham, working on the inositol 

 metabolism of the embryo, observed differences between the embryos 

 from Black and White Leghorn hens. Physico-chemical differences 

 between breeds of silkworm eggs are enumerated by Pigorini. 



The individual differences between eggs may be equally important. 

 Benjamin has shown that there are numerous variable factors which 

 modify the constitution of the egg. The amount of yolk, egg-white, 

 and water, as well as the thickness of the shell, vary according to 

 the season, diet, age (Riddle) and general condition of the bird 



