ISA PHYSIOLOGICAL GENETICS 



transplantations of testes with different combinations of the 

 two races. When an AA-testis is transplanted into an aa- 

 host, it remains pigmented, and the eyes of t lie host turn black; 

 the result is thru the same as in the two Drosophila cases com- 

 bined. (A transplantation is, of course, another method of 

 producing mosaics.) This primary experiment was then followed 

 up by Kuehn, Caspari, and Plagge (1935). The genes aa affect, 

 in fact, quite a number of characters in addition to eye color and 

 gonad color: the skin of the caterpillar is paler; the color of the 

 optic ganglia is more reddish (as opposed to brown); the amount 

 of pigment in the larval ocelli is changed; the velocity of develop- 

 ment and the vitality are decreased. This shows that the gene 

 in question acts all through development. For one character, 

 the pigmentation of the ocelli, it can be shown that a different 

 velocity of pigment formation is involved. Probably the same 

 applies also to the color of the ommatidia, which shows in 

 oo-individuals less and lighter pigment and smaller granules. 

 (There is also an intermediate allele a k with intermediate effects 

 existing.) As Caspari found, aa-testes transplanted into 

 A A -animals became dark; AA-testes in aa-animals remain dark. 

 AA-testes in aa-hosts make their eyes darken; but the result is 

 not exactly the same as in pure A A -eyes; the quantity of pig- 

 ment remains less than in the AA-type, and also the distribution 

 is somewhat different. Also, if these transplantations are made 

 sufficiently early, the larval pigment characters are influenced 

 correspondingly. The A A -testis then produces a substance 

 (or hormone) which acts all over the body. The testis is, how- 

 ever, not the only organ that produces this substance : implanted 

 ovaries act like testes, though less strongly; by implantation of 

 more than one ovary the effect is increased. The same effect, 

 but still weaker, may even be produced by transplantation of 

 brain. Most remarkable is finally the fact that this hormonic 

 effect may act upon the egg cell even before fertilization: if 

 aa-females contain transplanted AA-testes, their pure aa-offspring 

 may show the early pigmentation of the ocelli characteristic for 

 A A. The hormone then has entered the cytoplasm of the egg 

 within the ovary. (We may point out that here the procedure 

 has been reproduced that must be assumed to take place in the 

 cases of so-called maternal inheritance of Toyama (see page 206). 

 Especially does this last experiment show that the stuff produced 



