SEX CONTROL IN PIGEONS 



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The greater production of males in cattle— indicated 

 by Thury, Russell, and several others— from eggs that 

 have remained unfertilized for a period of hours, is al- 

 most certainly correlated with an increased water-content 

 which these eggs obtain before fertilization. We do not 

 know by direct observation that the ova of the cow takes 

 up water from the fluids that it meets in the reproductive 

 passages. We do know that this is true for the eggs of 

 every amphibian, reptile and bird that has been investi- 

 gated. Von der Stricht has, however, described phenom- 

 ena in the yolk granules of the extra-ovarian egg on one 

 mammal— the bat— which phenomena I am quite assured 

 from my own earlier studies on the yolk spheres, definitely 

 indicate that in this one mammal in which the data permit 

 a judgment, the egg does take up water from the fluid that 

 it meets in the Fallopian tube. There is good reason to 

 believe that the changed sex-ratios of cattle can be asso- 

 ciated with changes in the egg-metabolism effected 

 through, or connected with, differential water values. 



The important recent work of Baltzer convincingly 

 shows the plastic, fluid, controllable and reversible na- 

 ture of sex in Bonellia. And, it would be difficult to be- 

 lieve that the larva that attaches itself to the "riissel" 

 of an adult, then quickly and fully differentiates, and be- 

 comes a male, is not displaying a higher metabolism than 

 is the larva that rests for iong in the mud and sand, and 

 after prolonged growth becomes a female. Baltzer s 

 results deserve a much more extensive statement than 

 can be given here. 



Many points, too, in Geoffrey Smith's illuminating 

 studies on sex in the spider crabs would seem to be in har- 

 mony with the view that the castrated males progressively 

 lose their initial advantages of a higher metabolism, and 

 that thev then become more female-like as they approach 

 the lower metabolic levels which are normal to the fe- 

 males. Though Smith, so far as I am aware, has not 

 thus interpreted his results. 



The point to these citations is that sex control in the 

 several various forms in which it has been accomplished, 



