Description of the Modifications of certain Organs 



"whicb seem to be Illustrations of the luheritance of Acquired Oharacters 

 in Mammals aiid Birds. 



By 

 Hans Gadow, Ph. D., M. A., 



Slrickland-Curator and Lecturer ou advanced Morpbology of Vertebrata 

 in the University of Cambridge. 



With Plates XLIII and XLIV. 



„I may give another instance of a structure 

 which apparently owes its origin exclusively to 

 use or habit." 



Charles Darwin, Origin of Species. 



The eagerness with which the question of the inheritance of 

 acquired characters has been discussed within the last few years, and 

 the hitherto apparently unsuccessful attempts to bring forward cases 

 which can be used for a settlement of this question, has induced me 

 to collect a few instances which possibly raay help to throw some light 

 upon this Problem. 



As Professor Lankester has reeently stated (Nature, March 6"" 

 1890) the cases should be such „in which the transmission of acquired 

 characters is directly demonstrated", or „in which it seems impossible 

 to explain a given structure except on the assumption of the truth of 

 Lamarck's second law" ^). Moreover „we want well ascertained facts 

 and straightforward reasoning from facts." 



1) It will be convenient to repeat here the original wording of 

 Lamarck's second law: Tout ce que la nature a fait acqu^rir ou per- 

 dre aux individus par l'influence des circonstances oü leur race se 

 trouve depuis longtemps expos6, et par consöquent par l'influence de 

 r emploi predominant de tel organe, ou par celle d'un defaut constant 

 d usage de teile partie, eile le conserve par la generation aux nouveaux 



Zool. J.-ihrb. V. AMh. f. Syst. ^j 



