1917] ANIMAL PRODUCTION. 371 



" Regarding the offspring the results show that out of 12 different characters 

 for which we have exact quantitative data the offspring of treated parents 

 taken as a group are superior to the offspring of untreated parents in eight 

 characters. The offspring of untreated parents are superior to those of the 

 treated in respect of but two characters, and these are characters which are 

 quite highly correlated with each other and really should be counted as but 

 one single character. Finally with respect to two character groups there Is no 

 difference between the treated and the untreated." 



The author interprets the results of the investigation as showing that "(1) 

 there is no evidence that specific germinal changes have been induced by the 

 treatment, at least in those germ cells which produced zygotes; and (2) there 

 is no evidence that the germ cells whicli produced zygotes have in any respect 

 been injured or deleteriously affected." 



Studies on the physiology of reproduction in the domestic fowl. — XVI, 

 Double eggs, Maynie R. Curtis {Biol. Bui. Mai: Biol. Lab. Woods Hole, 31 

 (1916), No. 3, pp. 181-212, pis. 3, figs. 7; abs. in Maine Sta. Bui. 257 {1916), 

 pp. 3/i8-S51). — Double or inclosed eggs which were laid or found partly formed 

 within the oviduct at autopsy are described and their formation di.scussed from a 

 physiological standpoint. The specimens described are classified, according to 

 their general structure, into double eggs with the inclosing egg a normal egg and 

 the inclosed egg also normal or the inclosed egg a dwarf egg, and double eggs 

 in which the inclosing egg does not contain a yolk but is simply a set of egg 

 envelopes containing a normal egg or a dwarf egg. 



In all the specimens examined the yolk was contained in the blunt end and 

 the inclosed egg in the pointed end. Although one specimen has been described 

 in which the yolk was found in the pointed and the inclosed egg in the blunt 

 end of the inclosing egg, the accuracy of the observation is indicated as being 

 doubtful. 



The results of the study show that " a membrane-covered or hard-shelled 

 normal or dwarf egg may be returned up the duct and may either meet its 

 successor and return with it, becoming inclosed in a common set of egg 

 envelopes, or not meeting its successor it may again be forced through the duct 

 stimulating the secretion of a set of egg envelopes around itself. 



" The number of egg envelopes common to the inclosed egg and the yolk of 

 the inclosing egg or the number of egg envelopes which surround the inclosed 

 egg when the inclosing egg has no yolk depends apparently on the level of the 

 duct at which the inclosed egg resumes its normal direction toward the cloaca. 



" The inclosed egg is usually forced up the duct without turning on its axis, 

 but occasionally the poles are reversed. A similar reversal of poles sometimes 

 occurs in normal laying, and it seems probable that in both ca.ses this turning 

 takes place in the uterus when the first powerful contractions of the xiterus 

 brings the outwardly directed end of the egg slightly above the opening from 

 the shell gland into the vagina and taugentially against the curved caudo- 

 dorsal angle of the uterus. 



" The inclosed egg usually precedes its successor through the duct, and there- 

 fore usually lies in the pointed or anterior end of the inclosing egg, while the 

 yolk of the inclosing egg lies in the blunt or posterior end. . . . 



"A hard-shelled egg uncovered by membrane or albumin is sometimes found in 

 the body cavity or upper oviduct, while a hard-shelled egg inclosed within 

 another egg is not usually immediately surrounded by an egg membrane. It 

 would, therefore, seem that th3 egg does not cause the secretion of egg envelopes 

 around itself on its v. ay up the duct. Since, in the case of a double-yolked egg, 

 a second yolk closely following the first does stinmlate the secretion of the sue- 



