76 THE GENETIC AND 



vince, than his famous axiom, uttered in 1855 

 " Omnis cellula e cellula." That is unquestionably 

 the boldest generalisation to which the youthful, inde- 

 pendent Virchow ever attained, and one on which he 

 justly prided himself not a little. He himself re- 

 peatedly compared it with Harvey's saying, which 

 marked an epoch " Omne vivum ex ovo." But 

 neither of these axioms is universally correct. On 

 the contrary, we now know that every cell does not 

 necessarily originate from a cell, any more than that 

 every organic individual originates from an ovum. In 

 many cases true nucleated cells proceed from un-nu- 

 cleated cytods, as in the Gregarinae, Myxomycetse and 

 others. Nay more, the primordial organic cells could 

 only have originated in the first instance from non- 

 cellular plastides or monads by their homogeneous 

 plasson resolving itself into an internal nucleus and an 

 external protoplasm. Thus, as we subsequently learnt 

 to know most of the exceptions to this generalisation 

 of Virchow, it appeared all the bolder; the more 

 so as we were at that time far from being able to 

 refer all the different tissues of the higher animals 

 with any certainty to cells, and as not a few experi- 

 ments seemed to point to the hypothesis of free cell- 

 formation. That guiding axiom, which so powerfully 

 furthered the cell-theory, Virchow, from his present 

 standpoint, must wholly condemn as a crime against 



