ANIMAL I'HODUCTION. 71 



Zoologists. ;it I'.nltlniore, Doconibin-, 1!»0S, in wliicli are reported investigations 

 undertalven to determine the nature of the stiiunlns which excites the reflex 

 activity of the shell-secreting glands. 



"The oviduct was transected 1 or 2 cm. above the upper end of the 'shell 

 gland." The anterior i)ortion of the oviduct was then ligated. The intestine 

 was transected just anterior to the cloaca and the cloacal wall repaired I)y 

 inversion of the stump and a purse striug suture. Then the cut end of the 

 intestine was anastomosed to the cut end of the oviduct (' shell gland '). As a 

 result of this operation the feces must necessarily pass through the 'shell 

 gland ' on the way to the cloaca. In hens on which this operation has been 

 performed a calcareous shell is deposited on the feces during their passage 

 through the shell gland. The results obtained from these experiments are held 

 to warrant the following conclusions: 



"(1) The stimulus which sets the shell-secreting glands of the fowl's oviduct 

 into activity is mechanical rather than chemical in nature. 



"(2) The formation of a shell on the hen's egg is brought about by a strictly 

 local reflex, and is not immediately dependent upon the activity of other por- 

 tions of the reproductive system (nervous impulse of hormone formation)." 



A Mendelian view of sex heredity, W. E. Castle (Science, n. sci:, 29 ( 1009), 

 No. y.'fO, pp. 395-JfOO). — In this article the author suggests an hypothesis by 

 which the recent theories of Wilson, Correns, and Bateson on sex heredity are 

 apparently harmonized. From recent investigations there appears to be a 

 differential factor between male and female which is allelomorphic in the ab- 

 sence of that factor. It is inherited in Mendelian fashion and its presence is 

 dominant over absence. "As regard* the transmission of this factor we can 

 recognize two distinct categories of cases: 



"A. Femaleness is attained only when the differential factor is doubly repre- 

 sented in the individual. In such cases tlie female is a homozygote, and the 

 egg invariably transmits the differential factor. Sex determination then rests 

 with the male parent, for half tue spermatozoa possess the differential factor 

 and half lack it. The female is a homozygous dominant, not, as Correns sup- 

 posed, recessive; whereas the male is a heterozygous dominant, pure recessives 

 being unknown. 



" B. Femaleness is attained whenever the differential factor is present in one 

 only of the conjugating gametes which produce the individual. The gamete 

 which transmits tlie differential factor is of course the macrogamete (egg), 

 since this factor is not possessed by the male parent. The female is a hetero- 

 zygous dominant, the male a pure recessive; liomozygous dominants are 

 unknown. 



"The experimental proof for the existence of these two categories of cases 

 has been produced for class A by Correns, and for class B by Doncaster and 

 others. Cytological evidence which strongly supports the interpretation given to 

 class A has beeen produced by McClung, Stevens, Morgan and especially by 

 Wilson. This evidence is fully corroborated by the work of many others. 

 Direct cytological evidence for the existence of class B is not known at present, 

 but may confidently be looked for." 



The author points out the importance of reciprocal crosses in the study of 

 secondary sexual characters, and shows how it may be possible for these to be 

 more common in the male even though the male be considered a retrogressive 

 variation! 



Australian saltbush (Atriplex semibaccata) ; its com^position and digesti- 

 bility. Notes on Russian thistle, W. I'. Hkauuicn (Colorado Sta. liiil. IS.'), pit. 

 3-16). — This bulletin discusses the value of the Russian thistle and the native 



89616— No. 1—09 6 



