NOTICES OF BOOKS. xxxi 



and become independent — that is to say, instead of a common and cor- 

 relative development giving rise to one organism, an individualistic 

 segregation occurs amongst the first -formed cells and produces a 

 number of separate plants — and analogous cases are met with even 

 amongst gymnosperms. What nature has done in these plants man, 

 as already stated, can accomplish by the employment of special means, 

 in the case of some animals, though of course the results are not so 

 perfect. But in principle they are probably not dissimilar. 



To return to Dr. Hertwig's book, we find that he admits, as 

 essential to his theory of Biogenesis, the existence of two substances 

 which together make up the living substance. The first, the hereditary 

 and governing substance, he calls Idioplasm, following in Nageli's 

 footsteps, whilst he also postulates the existence of a " Formed matter" 

 (Beale) or Protoplasma-product. The latter is moulded by the idio- 

 plasm, and is caused by it to assume the particular character distinctive 

 of the various cells and tissues of the body. 



But this separation or distinction of the living substance into idio- 

 plasm and formed plasm is, under various guises, common to most of 

 the more recent theories put forward to explain the elvai and ytyveo-#ai of 

 organic life, nor do we find anything strikingly novel in the notions that 

 not only is the idioplasm the substance conserving the hereditary 

 qualities of the species, but that also it is capable of receiving im- 

 pressions from without, and thus, itself being altered, modifying its action 

 as the formative material of the cell. Indeed, Dr. Hertwig expressly ad- 

 mits the possibility of the inheritance of acquired character, but regards 

 such inheritance as an important fact with which his theory of Biogenesis 

 is competent to reckon. Nevertheless, the examples he quotes are 

 singularly unconvincing. That " attenuated " bacteria may reproduce 

 attenuated forms is really not to the purpose, since there is no sexual 

 propagation in these forms, but merely an increase of cells resulting from 

 vegetative activity. One might as well attempt to base an argument 

 as to the inheritance of acquired characters on the behaviour of a rose- 

 bush manured in one year and starved in the next. The rose-bush cells 

 will, it is true, not be the same in the successive seasons, but the 

 different results in the case of the new starved tissues have no sort of bear- 

 ing on the inheritance or non-inheritance of acquired characters in the 

 sense in which these are ordinarily defined and understood. And the 

 different bacterial generations are really analogous to the new genera- 

 tions of the rose-bush (somatic) cells. 



And the other instance quoted by the author in support of the 

 transmission of acquired characters seems, to the present writer, rather 

 to tell against the assumption that the hereditary substance — the idio- 

 plasm — was in any way really affected. This instance referred to is 

 derived from the researches of Ehrlich upon the action of Ricin on 

 mice. This investigator found that it was possible to immunise these 

 animals by slowly rendering them accustomed to the poison, and, 

 further, that this immunisation could be partially transmitted to the 



