TRANSMISSION IN UNICELLULARS 187 



spore-formation. What occurred in the cases referred to was 

 probably a temporary dislocation or disturbance of the character- 

 istic organisation of the cells, with the result that pigment pro- 

 duction was suppressed. When the inhibiting conditions were 

 removed the original organisation recovered itself in the course of 

 generations. But there is a great difference between such cases 

 and, let us say, the transmission of sun-burning, or of specially 

 strong muscles, or of a callosity on the skin, or a dwarfed form, 

 which are instances of bodily modifications, technically called 

 acquired characters. In the case of the bacilli the disturbed organi- 

 sation was halved or multiplied in each reproductive process, and 

 the effect originally induced was inherited from generation to 

 generation, eventually disappearing as the restoration of normal 

 conditions allowed the original organisation to re-assert itself in its 

 integrity ; in the case of the supposed inheritance of a callosity we 

 have to assume either that the influence which induced this, or the 

 influence of it after it had been induced, also affected the germinal 

 material in the reproductive organs in such a way that the contained 

 germ-cells, when liberated, developed into an organism with more 

 or less of the callosity. It must be evident, without further dis- 

 cussion, that the cases are not at all on a par, and that inheritance 

 in unicellulars has not been considered with sufficient carefulness 

 even by experts. 



Prof. L. Errera (1899) reported an experiment with a simple 

 but multicellular mould (Aspergillus niger), which adapted 

 itself to a medium more concentrated than the normal. The 

 second generation of the mould was more adapted than the first, 

 and the adaptation to the concentrated medium was not wholly 

 lost after rearing in the normal medium again. This looks like 

 evidence of the inheritance of the acquired adaptive quality 

 which was brought about as a direct modification. But the 

 case does not really help us, since the distinction between soma 

 and germ-plasm is not more than incipient in the mould in ques- 

 tion. And even if the distinction were more marked, it would 

 only show that the germ-plasm is capable of being affected along 

 with the body, by a deeply saturating influence, which nobody 

 as ever denied. 



