76 ALAN ARTHUR HOYDEN. 



between male and female Lepidopteran gonads by means of this 

 test. Many other attempts have been made to show an organ 

 specificity for the precipitin reaction but so far all this work has 

 failed of confirmation, except in the case of the lens of the 

 Vertebrate eye. 



As a matter of fact even the results of Uhlenhuth, Nuttall, 

 and Hektoen have not gone unchallenged. Strube (i9 O2 ) 

 Kister and Wolff (1902), and many others claimed that the 

 precipitin reaction was not always specific even in the quanti- 

 tative sense. And in more recent fears similar claims have 

 again been made. Thus Friedberger and Collier (1919) state 

 that an antiserum against one kind of protein may react \vith 

 equal or even greater intensity with non-related proteins. A 

 year later Friedberger and Jarre (1920) reported upon "aspecific 

 antisera" and claimed that many of the antisera which they 

 produced reacted without regard to the relationship of the 

 proteins used. Reese r (1919) independently in Holland claims 

 the same thing and is confirmed by Yu (1923) and again by 

 Friedberger and Meissner (1923) in Germany. 



Thus the matter stands to-day, the value of the precipitin 

 reaction in the study of animal relationships being by no means 

 completely established. For if the precipitin reaction does not 

 take place according to the relationship of the proteins tested, 

 as Friedberger claims, its results will always be of uncertain 

 value in such studies. 



One more problem that has been attacked with the aid of 

 immune reactions including the precipitin test should be men- 

 tioned. This is in the field of experimental evolution and the 

 work referred to is that of Guyer and Smith (1920). By in- 

 jecting antisera against rabbit lens into pregnant rabbits these 

 investigators have obtained hereditary eye defects which appeared 

 in many succeeding generations. Furthermore, just recently 

 Guyer (1925) has been able to demonstrate that by needling the 

 lens of rabbits lens defects may be caused in their young. The 



gnificance of these discoveries in the solution of problems of 

 experimental evolution may be almost unlimited. 



The precipitin reaction has ihcn com i United something to 

 >lution of at least two fundamental zoological problems, 



