JACQUES LOEB 361 



such embryos. This indicates that there exists in the blood of the 

 male cattle embryo an inhibitory substance which prevents the normal 

 development of the sex glands of the female embryo. 



A second case is that of the prevention of the development of the 

 male plumage in the female fowl. Boring and PearP have shown that 

 the ovary of such females contains specific cells, the lutear cells, 

 which are absent in the male. Boring and Morgan^ have found that 

 in the Sebright, where the male shows hen-feathering, lutear cells exist 

 in the testes of the male bird. Since extirpation of the ovary in fowl 

 and duck leads to the assumption of the full male plumage by the 

 female (Goodale^), it seems as if some specific substance in the ov- 

 ary inhibited the development of male plumage in the female. This 

 inhibitory substance may be contained in the lutear cells, which, 

 however, cannot well influence the development of feathers in any 

 other way than by the secretion of some substance into the blood. 

 The assumption that the inhibition of shoot formation in the basal 

 part of a stem by a leaf is due to an inhibitory substance secreted by 

 the leaf is therefore not without a precedent. 



It is, however, necessary to call attention to the fact that even 

 if the inhibitory influence of the leaf upon shoot formation should 

 turn out to be based on the chemical character of the sap sent out 

 by the leaf, it does not follow that all phenomena of inhibition and 

 correlation in regeneration will find their explanation on the same 

 basis. Quantitative experiments published in a former paper suggest 

 that the inhibitory influence of a piece of stem on shoot formation 

 in the leaf of Bryophyllum calycinum is due to the fact that the leaf 

 sends its sap normally to the stem, and that as long as this happens 

 the buds in the notches of the leaf cannot grow out.^" 



We shall show in the next communication that growing buds have 

 inhibitory influences upon the formation of shoots comparable to the 

 same influences caused by a leaf. 



^Boring, A. M., and Pearl, R., Anat. Rec, 1917, xiii, 253. Pearl and Boring, 

 Am. J. Anat., 1918, xxiii, 1. 



s Boring, A. M., and Morgan, T. H., /. Gen. Physiol., 1918, i, 127. 



''Goodale, H. D., Biol. Bull., 1910-11, xx, 35; Am. Nat., 1913, xlvii, 159; 

 /: Exp. ZooL, 1916, XX, 421. 

 ^^ Loeb, Ann. Inst. Pasteur, 1918, xxxii, 1. 



