No. 508] MECHANISM FOR ORGANIC CORRELATION 217 



duced to take on the growth characteristic of the early 

 stages of pregnancy though she is absolutely without 

 young. 



Another important set of bodily correlations are those 

 that exist between the reproductive glands and the sec- 

 ondary sexual organs such as the comb, hackles and spurs 

 of the common male fowl. It is well known that if the 

 genital glands of a young male fowl are removed before 

 it has attained maturity, it will fail to perfect its sec- 

 ondary sexual organs and the usual external evidences 

 of maleness may be absent. But if, as Shattock and 

 Seligmann have shown, a small piece of a male gland is 

 grafted into a young castrated male the comb, hackles, 

 and spurs may develop as in a normal bird. It is, there- 

 fore, highly probable that the reproductive glands, like 

 the ductless glands, produce hormones by which the de- 

 velopment of the secondary sexual organs is determined. 



Not only are hormones produced in the adult body, 

 but they are very probably formed during development. 

 Such at least seems to be the condition in the correlated 

 growth of the vertebrate eye and its lens. As is well 

 known, the eyeball in the vertebrate is formed around 

 an outgrowth from the brain ; the lens is developed from 

 the skin in such a position as to fit the forming ball. This 

 interesting correlation in position between the external 

 lens and the deep-seated eyeball has been made clear by 

 Lewis who has shown that when the forming eyeball of 

 a given species of frog is covered by grafting over it skin 

 from the abdominal region of even another species of 

 frog, this foreign abdominal skin will begin to form a 

 lens in an appropriate position for the underlying eye- 

 ball. Apparently the eyeball gives out a substance, a 

 hormone, that so influences the adjacent skin that, irre- 

 spective of its source within certain limits, it forms a 

 lens. Thus embryonic correlations may also depend 

 upon hormones. 



These numerous examples show that many organs of 

 the body produce hormones that profoundly affect the 



