Review: Xenia in Fowls 



213 



not of a nature to show itself. The 

 phenomenon of xenia in the plant world, 

 then, is a perfectly simple and natural 

 one, is dependent on the double fertiliza- 

 tion described above, which occurs in 

 all flowering plants, and may be ex- 

 pected to be visable whenever the differ- 

 ences between the two parents are of a 

 nature favorable to its observation. 



There is always the hope in genetics 

 that what is found to be true of one 

 section of the organic world will be found 

 to hold good in all. If xenia occurred 

 in plants, it or something like it might 

 be expected in animals. Accordingly, 

 phenomena of similar nature in the 

 animal kingdom were sought. 



An attempt was made to connect 

 xenia with telegony,^ but the analogy 

 does not seem to be very close. There 

 is, in fact, a fundamental difference, 

 for in xenia we have an actual union 

 of two cell-nuclei, while the supposed 

 effects of telegony have been accredited 

 to an interchange of blood, or some 

 more mystical and less definable cause. 

 Telegony is now dead, in scientific 

 circles, while plant xenia is more alive 

 than ever. 



If it could not be traced in mammals, 

 it might be traced in fowls. It has 

 long been believed by some people, 

 though not by rnost naturalists, that 

 the eggs laid by a hen are influenced, 

 as to size, shape, color, by the cock 

 with which she is mated. An attempt 

 was made on numerous occasions to 

 show telegony in this connection, but 

 the case was very weak. Then it 

 was decided, by a certain set of investi- 

 gators, that here was the long-sought 

 case of xenia in the animal kingdom. 



From this standpoint the question 

 has been debated with considerable 

 warmth during recent years, princi- 

 pally among German biologists. Obvi- 

 ously, there are two parts to the dis- 

 cussion. First, does the alleged influ- 

 ence of the cock on the appearance of 

 the hen's eggs really exist' If it does 



not, there is an end of the dispute; 

 but if it does, we can go one step farther, 

 and try to explain it. If it exists, is it 

 a phenomenon similar to xenia in plants, 

 or must it be explained in some other 

 way? The latter question may be 

 set aside until we have considered 

 whether there is any evidence of this 

 paternal influence on hens' eggs. 



XENIA IN POULTRY 



The first observation on record by a 

 man of science seems to go back to 

 W. von Nathusius (1867) who reported 

 the case of a supposedly pure bred hen, 

 of a breed that always produced white 

 eggs. She was mated to a cock of the 

 old Cochin China breed, which pro- 

 duces brown-shelled eggs, and some 

 days later she began to lay eggs with 

 yellowish shells. This influence dis- 

 appeared very gradually; even after 

 months an occasional dark egg appeared. 



Such evidence, of course, counts for 

 little with the modern biologist, who 

 has become more critical than a jury 

 lawyer as to what he accepts. There 

 were a dozen ways in which the facts, 

 if such they were, might be explained, 

 and as there had been no "control" 

 of any kind, there was no means of 

 knowing that the yellowish color of 

 the eggs was not due to something in the 

 hen's food, or to any one of niimerous 

 other exterior or interior causes, quite 

 independently of the Cochin China 

 cock. So an attempt was made to 

 gather evidence of greater "evidential 

 value" by carefully planned experi- 

 ments. 



Plymouth Rocks, a breed well known 

 to lay brown-shelled eggs, were chosen 

 by Professor P. Holdefleiss^ of the 

 University of Halle for this purpose, 

 and mated with a Leghorn cock, whose 

 breed produces eggs of a pure white. 

 "The eggs showed a series of colors 

 from dark brown to white. Some of 

 the medium brown eggs showed white 

 flecks. Some of the dark brown were 



1 The principle of telegony " is that females are impregnated by the first males to which they are 

 bred, so that all their subsequent offspring, regardless of their actual father, will show influence 

 of the first male." See "Telegony," by Dr. Etienne Rabaud, Journal of Heredity, V, 9, 389-399, 

 Washington, D. C, September, 1914. 



- Holdefleiss, P., in Ber. aus dem phvsiol. Lab. u. der Versuchsanstalt d. landw. Inst. d. 

 Univ. Halle, 20 Heft, 1911, S. 93-111; also in 25 Flugschrift d. D. Ges. f. Ziichtungskunde, Berlin, 

 1913. 



