THE PHENOMENA OF REVERSION 3OI 



forms, and if in a few generations thousands of specimens of its 

 offspring are raised, it will always be found that scarcely two of 

 them are alike. Some revert to the paternal and some to the 

 maternal form, while others, again, are intermediate between 

 the two. The remainder present the most varied alternation of 

 paternal and maternal characteristics, and show almost every 

 degree of mutual intermingling.' 



De Vries states this merely as a proof of what he calls the 

 'free miscibility of the characters,' without attaching importance 

 to the fact that the hybrids of the first generation behave quite 

 differently from those of the second, or attempting to account 

 for this fact theoretically. 



Professor Liebscher * has recently brought forward the fol- 

 lowing interesting instance, in which the details were very 

 accurately investigated. He crossed two species of barley, 

 Hordeum steiidelii 9 and Horde^ini trifurcatum $ , in the for- 

 mer of whicli the spikelets are arranged in two rows and are 

 black, while in the latter they are arranged in four rows and are 

 white. The hybrid is as nearly as possible intermediate between 

 the two forms, ' allilie ears, moreover, ^ being strikingly uniform^ 

 as one would be led to expect theoretically. In all the hybrids 

 the spikelets are arranged in two rows, and in the main spike- 

 lets the tips are black, while in the lateral ones they are white, 

 and the ' Loffel ' — which are peculiar to Hordeietn trifnrcattmi — 

 are black and white. The offspring produced from these hybrids 

 were exceedingly variable in the first, as well as in the second 

 generation . 



Liebscher has attempted to account for this variability by 

 assuming that a 'loosening ('Lockerung') of the structure of 

 the germ-plasm,' as well as ' re-combination of the individual 

 characters,' is produced by the process of reproduction. The 

 former results in 'a weakening of the power of faithful trans- 

 mission in the generative products,' i.e., -an inclination to 

 individual variation in the descendants.' This statement indi- 

 cates that Liebscher certainly had some kind of idea of the 

 actual process which occurs in tlie idioplasm, although it is not 

 made clear in what this 'loosening' consists. 



A definite meaning, however, underlies this expression as 

 soon as it is recognised that the germ-plasm consists of a large 



* Liebscher, ' Vererbung,' etc., Jen. Zeitschrift, Bd. 23, 1888. 



